Network Working Group                                      K. McCloghrie
Request for Comments: 2233                                 Cisco Systems
Obsoletes: 1573                                            F. Kastenholz
Category: Standards Track                                   FTP Software
                                                          November 1997


                 The Interfaces Group MIB using SMIv2


Status of this Memo

  This document specifies an Internet standards track protocol for the
  Internet community, and requests discussion and suggestions for
  improvements.  Please refer to the current edition of the "Internet
  Official Protocol Standards" (STD 1) for the standardization state
  and status of this protocol.  Distribution of this memo is unlimited.

Copyright Notice

  Copyright (C) The Internet Society (1997).  All Rights Reserved.

Table of Contents

  1 Introduction ..............................................    2
  2 The SNMP Network Management Framework .....................    2
  2.1 Object Definitions ......................................    3
  3 Experience with the Interfaces Group ......................    3
  3.1 Clarifications/Revisions ................................    3
  3.1.1 Interface Sub-Layers ..................................    4
  3.1.2 Guidance on Defining Sub-layers .......................    6
  3.1.3 Virtual Circuits ......................................    8
  3.1.4 Bit, Character, and Fixed-Length Interfaces ...........    8
  3.1.5 Interface Numbering ...................................   10
  3.1.6 Counter Size ..........................................   14
  3.1.7 Interface Speed .......................................   16
  3.1.8 Multicast/Broadcast Counters ..........................   17
  3.1.9 Trap Enable ...........................................   18
  3.1.10 Addition of New ifType values ........................   18
  3.1.11 InterfaceIndex Textual Convention ....................   18
  3.1.12 New states for IfOperStatus ..........................   19
  3.1.13 IfAdminStatus and IfOperStatus .......................   20
  3.1.14 IfOperStatus in an Interface Stack ...................   21
  3.1.15 Traps ................................................   21
  3.1.16 ifSpecific ...........................................   23
  3.1.17 Creation/Deletion of Interfaces ......................   24
  3.1.18 All Values Must be Known .............................   24
  4 Media-Specific MIB Applicability ..........................   25



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  5 Overview ..................................................   26
  6 Interfaces Group Definitions ..............................   26
  7 Acknowledgements ..........................................   64
  8 References ................................................   64
  9 Security Considerations ...................................   65
  10 Authors' Addresses .......................................   65
  11 Full Copyright Statement .................................   66

1.  Introduction

  This memo defines a portion of the Management Information Base
  (MIB) for use with network management protocols in the Internet
  community.  In particular, it describes managed objects used for
  managing Network Interfaces.

  This memo discusses the 'interfaces' group of MIB-II, especially the
  experience gained from the definition of numerous media- specific MIB
  modules for use in conjunction with the 'interfaces' group for
  managing various sub-layers beneath the internetwork- layer.  It
  specifies clarifications to, and extensions of, the architectural
  issues within the previous model used for the 'interfaces' group.

  This memo also includes a MIB module.  As well as including new
  MIB definitions to support the architectural extensions, this MIB
  module also re-specifies the 'interfaces' group of MIB-II in a
  manner that is both compliant to the SNMPv2 SMI and semantically-
  identical to the existing SNMPv1-based definitions.

  The key words "MUST" and "MUST NOT" in this document are to be
  interpreted as described in RFC 2119 [10].

2.  The SNMP Network Management Framework

  The SNMP Network Management Framework presently consists of three
  major components.  They are:

  o    RFC 1902 which defines the SMI, the mechanisms used for
       describing and naming objects for the purpose of management.

  o    STD 17, RFC 1213 defines MIB-II, the core set of managed
       objects for the Internet suite of protocols.

  o    STD 15, RFC 1157 and RFC 1905 which define two versions of
       the protocol used for network access to managed objects.







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  The Framework permits new objects to be defined for the purpose of
  experimentation and evaluation.

2.1.  Object Definitions

  Managed objects are accessed via a virtual information store,
  termed the Management Information Base or MIB.  Objects in the MIB
  are defined using the subset of Abstract Syntax Notation One
  (ASN.1) defined in the SMI.  In particular, each object object
  type is named by an OBJECT IDENTIFIER, an administratively
  assigned name.  The object type together with an object instance
  serves to uniquely identify a specific instantiation of the
  object.  For human convenience, we often use a textual string,
  termed the descriptor, to refer to the object type.

3.  Experience with the Interfaces Group

  One of the strengths of internetwork-layer protocols such as IP
  [6] is that they are designed to run over any network interface.
  In achieving this, IP considers any and all protocols it runs over
  as a single "network interface" layer.  A similar view is taken by
  other internetwork-layer protocols.  This concept is represented
  in MIB-II by the 'interfaces' group which defines a generic set of
  managed objects such that any network interface can be managed in
  an interface-independent manner through these managed objects.
  The 'interfaces' group provides the means for additional managed
  objects specific to particular types of network interface (e.g., a
  specific medium such as Ethernet) to be defined as extensions to
  the 'interfaces' group for media-specific management.  Since the
  standardization of MIB-II, many such media-specific MIB modules
  have been defined.

  Experience in defining these media-specific MIB modules has shown
  that the model defined by MIB-II is too simplistic and/or static
  for some types of media-specific management.  As a result, some of
  these media-specific MIB modules assume an evolution or loosening
  of the model.  This memo documents and standardizes that evolution
  of the model and fills in the gaps caused by that evolution.  This
  memo also incorporates the interfaces group extensions documented
  in RFC 1229 [7].

3.1.  Clarifications/Revisions

  There are several areas for which experience has indicated that
  clarification, revision, or extension of the model would be
  helpful.  The following sections discuss the changes in the
  interfaces group adopted by this memo in each of these areas.




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  In some sections, one or more paragraphs contain discussion of
  rejected alternatives to the model adopted in this memo.  Readers
  not familiar with the MIB-II model and not interested in the
  rationale behind the new model may want to skip these paragraphs.

3.1.1.  Interface Sub-Layers

  Experience in defining media-specific management information has
  shown the need to distinguish between the multiple sub-layers
  beneath the internetwork-layer.  In addition, there is a need to
  manage these sub-layers in devices (e.g., MAC-layer bridges) which
  are unaware of which, if any, internetwork protocols run over
  these sub-layers.  As such, a model of having a single conceptual
  row in the interfaces table (MIB-II's ifTable) represent a whole
  interface underneath the internetwork-layer, and having a single
  associated media-specific MIB module (referenced via the ifType
  object) is too simplistic.  A further problem arises with the
  value of the ifType object which has enumerated values for each
  type of interface.

  Consider, for example, an interface with PPP running over an HDLC
  link which uses a RS232-like connector.  Each of these sub-layers
  has its own media-specific MIB module.  If all of this is
  represented by a single conceptual row in the ifTable, then an
  enumerated value for ifType is needed for that specific
  combination which maps to the specific combination of media-
  specific MIBs.  Furthermore, such a model still lacks a method to
  describe the relationship of all the sub-layers of the MIB stack.

  An associated problem is that of upward and downward multiplexing
  of the sub-layers.  An example of upward multiplexing is MLP
  (Multi-Link-Procedure) which provides load-sharing over several
  serial lines by appearing as a single point-to-point link to the
  sub-layer(s) above.  An example of downward multiplexing would be
  several instances of PPP, each framed within a separate X.25
  virtual circuit, all of which run over one fractional T1 channel,
  concurrently with other uses of the T1 link.  The MIB structure
  must allow these sorts of relationships to be described.

  Several solutions for representing multiple sub-layers were
  rejected.  One was to retain the concept of one conceptual row for
  all the sub-layers of an interface and have each media-specific
  MIB module identify its "superior" and "subordinate" sub-layers
  through OBJECT IDENTIFIER "pointers".  This scheme would have
  several drawbacks: the superior/subordinate pointers would be
  contained in the media-specific MIB modules; thus, a manager could
  not learn the structure of an interface without inspecting
  multiple pointers in different MIB modules; this would be overly



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  complex and only possible if the manager had knowledge of all the
  relevant media-specific MIB modules; MIB modules would all need to
  be retrofitted with these new "pointers"; this scheme would not
  adequately address the problem of upward and downward
  multiplexing; and finally, enumerated values of ifType would be
  needed for each combination of sub-layers.  Another rejected
  solution also retained the concept of one conceptual row for all
  the sub-layers of an interface but had a new separate MIB table to
  identify the "superior" and "subordinate" sub-layers and to
  contain OBJECT IDENTIFIER "pointers" to the media-specific MIB
  module for each sub-layer.  Effectively, one conceptual row in the
  ifTable would represent each combination of sub-layers between the
  internetwork-layer and the wire.  While this scheme has fewer
  drawbacks, it still would not support downward multiplexing, such
  as PPP over MLP: observe that MLP makes two (or more) serial
  lines appear to the layers above as a single physical interface,
  and thus PPP over MLP should appear to the internetwork-layer as a
  single interface; in contrast, this scheme would result in two (or
  more) conceptual rows in the ifTable, both of which the
  internetwork-layer would run over.  This scheme would also require
  enumerated values of ifType for each combination of sub-layers.

  The solution adopted by this memo is to have an individual
  conceptual row in the ifTable to represent each sub-layer, and
  have a new separate MIB table (the ifStackTable, see section 6
  below) to identify the "superior" and "subordinate" sub-layers
  through INTEGER "pointers" to the appropriate conceptual rows in
  the ifTable.  This solution supports both upward and downward
  multiplexing, allows the IANAifType to Media-Specific MIB mapping
  to identify the media-specific MIB module for that sub-layer, such
  that the new table need only be referenced to obtain information
  about layering, and it only requires enumerated values of ifType
  for each sub-layer, not for combinations of them.  However, it
  does require that the descriptions of some objects in the ifTable
  (specifically, ifType, ifPhysAddress, ifInUcastPkts, and
  ifOutUcastPkts) be generalized so as to apply to any sub-layer
  (rather than only to a sub-layer immediately beneath the network
  layer as previously), plus some (specifically, ifSpeed) which need
  to have appropriate values identified for use when a generalized
  definition does not apply to a particular sub-layer.

  In addition, this adopted solution makes no requirement that a
  device, in which a sub-layer is instrumented by a conceptual row
  of the ifTable, be aware of whether an internetwork protocol runs
  on top of (i.e., at some layer above) that sub-layer.  In fact,
  the counters of packets received on an interface are defined as
  counting the number "delivered to a higher-layer protocol".  This
  meaning of "higher-layer" includes:



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  (1)  Delivery to a forwarding module which accepts
       packets/frames/octets and forwards them on at the same
       protocol layer.  For example, for the purposes of this
       definition, the forwarding module of a MAC-layer bridge is
       considered as a "higher-layer" to the MAC-layer of each port
       on the bridge.

  (2)  Delivery to a higher sub-layer within a interface stack.  For
       example, for the purposes of this definition, if a PPP module
       operated directly over a serial interface, the PPP module
       would be considered the higher sub-layer to the serial
       interface.

  (3)  Delivery to a higher protocol layer which does not do packet
       forwarding for sub-layers that are "at the top of" the
       interface stack.  For example, for the purposes of this
       definition, the local IP module would be considered the
       higher layer to a SLIP serial interface.

  Similarly, for output, the counters of packets transmitted out an
  interface are defined as counting the number "that higher-level
  protocols requested to be transmitted".  This meaning of "higher-
  layer" includes:

  (1)  A forwarding module, at the same protocol layer, which
       transmits packets/frames/octets that were received on an
       different interface.  For example, for the purposes of this
       definition, the forwarding module of a MAC-layer bridge is
       considered as a "higher-layer" to the MAC-layer of each port
       on the bridge.

  (2)  The next higher sub-layer within an interface stack.  For
       example, for the purposes of this definition, if a PPP module
       operated directly over a serial interface, the PPP module
       would be a "higher layer" to the serial interface.

  (3)  For sub-layers that are "at the top of" the interface stack,
       a higher element in the network protocol stack.  For example,
       for the purposes of this definition, the local IP module
       would be considered the higher layer to an Ethernet
       interface.

3.1.2.  Guidance on Defining Sub-layers

  The designer of a media-specific MIB must decide whether to divide
  the interface into sub-layers or not, and if so, how to make the
  divisions.  The following guidance is offered to assist the
  media-specific MIB designer in these decisions.



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  In general, the number of entries in the ifTable should be kept to
  the minimum required for network management.  In particular, a
  group of related interfaces should be treated as a single
  interface with one entry in the ifTable providing that:

  (1)  None of the group of interfaces performs multiplexing for any
       other interface in the agent,
  (2)  There is a meaningful and useful way for all of the ifTable's
       information (e.g., the counters, and the status variables),
       and all of the ifTable's capabilities (e.g., write access to
       ifAdminStatus), to apply to the group of interfaces as a
       whole.

  Under these circumstances, there should be one entry in the
  ifTable for such a group of interfaces, and any internal structure
  which needs to be represented to network management should be
  captured in a MIB module specific to the particular type of
  interface.

  Note that application of bullet 2 above to the ifTable's ifType
  object requires that there is a meaningful media-specific MIB and
  a meaningful ifType value which apply to the group of interfaces
  as a whole.  For example, it is not appropriate to treat an HDLC
  sub-layer and an RS-232 sub-layer as a single ifTable entry when
  the media-specific MIBs and the ifType values for HDLC and RS-232
  are separate (rather than combined).

  Subject to the above, it is appropriate to assign an ifIndex value
  to any interface that can occur in an interface stack (in the
  ifStackTable) where the bottom of the stack is a physical
  interface (ifConnectorPresent has the value 'true') and there is a
  layer-3 or other application that "points down" to the top of this
  stack.  An example of an application that points down to the top
  of the stack is the Character MIB [9].

  Note that the sub-layers of an interface on one device will
  sometimes be different from the sub-layers of the interconnected
  interface of another device; for example, for a frame-relay DTE
  interface connected a frameRelayService interface, the inter-
  connected DTE and DCE interfaces have different ifType values and
  media-specific MIBs.

  These guidelines are just that, guidelines.  The designer of a
  media-specific MIB is free to lay out the MIB in whatever SMI
  conformant manner is desired.  However, in doing so, the media-
  specific MIB MUST completely specify the sub-layering model used
  for the MIB, and provide the assumptions, reasoning, and rationale
  used to develop that model.



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3.1.3.  Virtual Circuits

  Several of the sub-layers for which media-specific MIB modules
  have been defined are connection oriented (e.g., Frame Relay,
  X.25).  Experience has shown that each effort to define such a MIB
  module revisits the question of whether separate conceptual rows
  in the ifTable are needed for each virtual circuit.  Most, if not
  all, of these efforts to date have decided to have all virtual
  circuits reference a single conceptual row in the ifTable.

  This memo strongly recommends that connection-oriented sub-layers
  do not have a conceptual row in the ifTable for each virtual
  circuit.  This avoids the proliferation of conceptual rows,
  especially those which have considerable redundant information.
  (Note, as a comparison, that connection-less sub-layers do not
  have conceptual rows for each remote address.)  There may,
  however, be circumstances under which it is appropriate for a
  virtual circuit of a connection-oriented sub-layer to have its own
  conceptual row in the ifTable; an example of this might be PPP
  over an X.25 virtual circuit.  The MIB in section 6 of this memo
  supports such circumstances.

  If a media-specific MIB wishes to assign an entry in the ifTable
  to each virtual circuit, the MIB designer must present the
  rationale for this decision in the media-specific MIB's
  specification.

3.1.4.  Bit, Character, and Fixed-Length Interfaces

  RS-232 is an example of a character-oriented sub-layer over which
  (e.g., through use of PPP) IP datagrams can be sent.  Due to the
  packet-based nature of many of the objects in the ifTable,
  experience has shown that it is not appropriate to have a
  character-oriented sub-layer represented by a whole conceptual row
  in the ifTable.

  Experience has also shown that it is sometimes desirable to have
  some management information for bit-oriented interfaces, which are
  similarly difficult to represent by a whole conceptual row in the
  ifTable.  For example, to manage the channels of a DS1 circuit,
  where only some of the channels are carrying packet-based data.

  A further complication is that some subnetwork technologies
  transmit data in fixed length transmission units.  One example of
  such a technology is cell relay, and in particular Asynchronous
  Transfer Mode (ATM), which transmits data in fixed-length cells.
  Representing such a interface as a packet-based interface produces




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  redundant objects if the relationship between the number of
  packets and the number of octets in either direction is fixed by
  the size of the transmission unit (e.g., the size of a cell).

  About half the objects in the ifTable are applicable to every type
  of interface: packet-oriented, character-oriented, and bit-
  oriented.  Of the other half, two are applicable to both
  character-oriented and packet-oriented interfaces, and the rest
  are applicable only to packet-oriented interfaces.  Thus, while it
  is desirable for consistency to be able to represent any/all types
  of interfaces in the ifTable, it is not possible to implement the
  full ifTable for bit- and character-oriented sub-layers.

  A rejected solution to this problem would be to split the ifTable
  into two (or more) new MIB tables, one of which would contain
  objects that are relevant only to packet-oriented interfaces
  (e.g., PPP), and another that may be used by all interfaces.  This
  is highly undesirable since it would require changes in every
  agent implementing the ifTable (i.e., just about every existing
  SNMP agent).

  The solution adopted in this memo builds upon the fact that
  compliance statements in SNMPv2 (in contrast to SNMPv1) refer to
  object groups, where object groups are explicitly defined by
  listing the objects they contain.  Thus, in SNMPv2, multiple
  compliance statements can be specified, one for all interfaces and
  additional ones for specific types of interfaces.  The separate
  compliance statements can be based on separate object groups,
  where the object group for all interfaces can contain only those
  objects from the ifTable which are appropriate for every type of
  interfaces.  Using this solution, every sub-layer can have its own
  conceptual row in the ifTable.

  Thus, section 6 of this memo contains definitions of the objects
  of the existing 'interfaces' group of MIB-II, in a manner which is
  both SNMPv2-compliant and semantically-equivalent to the existing
  MIB-II definitions.  With equivalent semantics, and with the BER
  ("on the wire") encodings unchanged, these definitions retain the
  same OBJECT IDENTIFIER values as assigned by MIB-II.  Thus, in
  general, no rewrite of existing agents which conform to MIB-II and
  the ifExtensions MIB is required.

  In addition, this memo defines several object groups for the
  purposes of defining which objects apply to which types of
  interface:






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  (1)  the ifGeneralInformationGroup.  This group contains those
       objects applicable to all types of network interfaces,
       including bit-oriented interfaces.

  (2)  the ifPacketGroup.  This group contains those objects
       applicable to packet-oriented network interfaces.

  (3)  the ifFixedLengthGroup.  This group contains the objects
       applicable not only to character-oriented interfaces, such as
       RS-232, but also to those subnetwork technologies, such as
       cell-relay/ATM, which transmit data in fixed length
       transmission units.  As well as the octet counters, there are
       also a few other counters (e.g., the error counters) which
       are useful for this type of interface, but are currently
       defined as being packet-oriented.  To accommodate this, the
       definitions of these counters are generalized to apply to
       character-oriented interfaces and fixed-length-transmission
       interfaces.

  It should be noted that the octet counters in the ifTable
  aggregate octet counts for unicast and non-unicast packets into a
  single octet counter per direction (received/transmitted).  Thus,
  with the above definition of fixed-length-transmission interfaces,
  where such interfaces which support non-unicast packets, separate
  counts of unicast and multicast/broadcast transmissions can only
  be maintained in a media-specific MIB module.

3.1.5.  Interface Numbering

  MIB-II defines an object, ifNumber, whose value represents:

       "The number of network interfaces (regardless of their
       current state) present on this system."

  Each interface is identified by a unique value of the ifIndex
  object, and the description of ifIndex constrains its value as
  follows:

       "Its value ranges between 1 and the value of ifNumber.  The
       value for each interface must remain constant at least from
       one re-initialization of the entity's network management
       system to the next re-initialization."

  This constancy requirement on the value of ifIndex for a
  particular interface is vital for efficient management.  However,
  an increasing number of devices allow for the dynamic
  addition/removal of network interfaces.  One example of this is a
  dynamic ability to configure the use of SLIP/PPP over a



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  character-oriented port.  For such dynamic additions/removals, the
  combination of the constancy requirement and the restriction that
  the value of ifIndex is less than ifNumber is problematic.

  Redefining ifNumber to be the largest value of ifIndex was
  rejected since it would not help.  Such a re-definition would
  require ifNumber to be deprecated and the utility of the redefined
  object would be questionable.  Alternatively, ifNumber could be
  deprecated and not replaced.  However, the deprecation of ifNumber
  would require a change to that portion of ifIndex's definition
  which refers to ifNumber.  So, since the definition of ifIndex
  must be changed anyway in order to solve the problem, changes to
  ifNumber do not benefit the solution.

  The solution adopted in this memo is just to delete the
  requirement that the value of ifIndex must be less than the value
  of ifNumber, and to retain ifNumber with its current definition.
  This is a minor change in the semantics of ifIndex; however, all
  existing agent implementations conform to this new definition, and
  in the interests of not requiring changes to existing agent
  implementations and to the many existing media-specific MIBs, this
  memo assumes that this change does not require ifIndex to be
  deprecated.  Experience indicates that this assumption does
  "break" a few management applications, but this is considered
  preferable to breaking all agent implementations.

  This solution also results in the possibility of "holes" in the
  ifTable, i.e., the ifIndex values of conceptual rows in the
  ifTable are not necessarily contiguous, but SNMP's GetNext (and
  SNMPv2's GetBulk) operation easily deals with such holes.  The
  value of ifNumber still represents the number of conceptual rows,
  which increases/decreases as new interfaces are dynamically
  added/removed.

  The requirement for constancy (between re-initializations) of an
  interface's ifIndex value is met by requiring that after an
  interface is dynamically removed, its ifIndex value is not re-used
  by a *different* dynamically added interface until after the
  following re-initialization of the network management system.
  This avoids the need for assignment (in advance) of ifIndex values
  for all possible interfaces that might be added dynamically.  The
  exact meaning of a "different" interface is hard to define, and
  there will be gray areas.  Any firm definition in this document
  would likely to turn out to be inadequate.  Instead, implementors
  must choose what it means in their particular situation, subject
  to the following rules:





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  (1)  a previously-unused value of ifIndex must be assigned to a
       dynamically added interface if an agent has no knowledge of
       whether the interface is the "same" or "different" to a
       previously incarnated interface.

  (2)  a management station, not noticing that an interface has gone
       away and another has come into existence, must not be
       confused when calculating the difference between the counter
       values retrieved on successive polls for a particular ifIndex
       value.

  When the new interface is the same as an old interface, but a
  discontinuity in the value of the interface's counters cannot be
  avoided, the ifTable has (until now) required that a new ifIndex
  value be assigned to the returning interface.  That is, either all
  counter values have had to be retained during the absence of an
  interface in order to use the same ifIndex value on that
  interface's return, or else a new ifIndex value has had to be
  assigned to the returning interface.  Both alternatives have
  proved to be burdensome to some implementations:

  (1)  maintaining the counter values may not be possible (e.g., if
       they are maintained on removable hardware),

  (2)  using a new ifIndex value presents extra work for management
       applications.  While the potential need for such extra work
       is unavoidable on agent re-initializations, it is desirable
       to avoid it between re-initializations.

  To address this, a new object, ifCounterDiscontinuityTime, has
  been defined to record the time of the last discontinuity in an
  interface's counters.  By monitoring the value of this new object,
  a management application can now detect counter discontinuities
  without the ifIndex value of the interface being changed.  Thus,
  an agent which implements this new object should, when a new
  interface is the same as an old interface, retain that interface's
  ifIndex value and update if necessary the interface's value of
  ifCounterDiscontinuityTime.  With this new object, a management
  application must, when calculating differences between counter
  values retrieved on successive polls, discard any calculated
  difference for which the value of ifCounterDiscontinuityTime is
  different for the two polls.  (Note that this test must be
  performed in addition to the normal checking of sysUpTime to
  detect an agent re-initialization.)  Since such discards are a
  waste of network management processing and bandwidth, an agent
  should not update the value of ifCounterDiscontinuityTime unless
  absolutely necessary.




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  While defining this new object is a change in the semantics of the
  ifTable counter objects, it is impractical to deprecate and
  redefine all these counters because of their wide deployment and
  importance.  Also, a survey of implementations indicates that many
  agents and management applications do not correctly implement this
  aspect of the current semantics (because of the burdensome issues
  mentioned above), such that the practical implications of such a
  change is small.  Thus, this breach of the SMI's rules is
  considered to be acceptable.

  Note, however, that the addition of ifCounterDiscontinuityTime
  does not change the fact that:

       It is necessary at certain times for the assignment of ifIndex
       values to change on a reinitialization of the agent (such as a
       reboot).

  The possibility of ifIndex value re-assignment must be
  accommodated by a management application whenever the value of
  sysUpTime is reset to zero.

  Note also that some agents support multiple "naming scopes", e.g.,
  for an SNMPv1 agent, multiple values of the SNMPv1 community
  string.  For such an agent (e.g., a CNM agent which supports a
  different subset of interfaces for different customers), there is
  no required relationship between the ifIndex values which identify
  interfaces in one naming scope and those which identify interfaces
  in another naming scope.  It is the agent's choice as to whether
  the same or different ifIndex values identify the same or
  different interfaces in different naming scopes.

  Because of the restriction of the value of ifIndex to be less than
  ifNumber, interfaces have been numbered with small integer values.
  This has led to the ability by humans to use the ifIndex values as
  (somewhat) user-friendly names for network interfaces (e.g.,
  "interface number 3").  With the relaxation of the restriction on
  the value of ifIndex, there is now the possibility that ifIndex
  values could be assigned as very large numbers (e.g., memory
  addresses).  Such numbers would be much less user-friendly.
  Therefore, this memo recommends that ifIndex values still be
  assigned as (relatively) small integer values starting at 1, even
  though the values in use at any one time are not necessarily
  contiguous.  (Note that this makes remembering which values have
  been assigned easy for agents which dynamically add new
  interfaces).






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  A new problem is introduced by representing each sub-layer as an
  ifTable entry.  Previously, there usually was a simple, direct,
  mapping of interfaces to the physical ports on systems.  This
  mapping would be based on the ifIndex value.  However, by having
  an ifTable entry for each interface sub-layer, mapping from
  interfaces to physical ports becomes increasingly problematic.

  To address this issue, a new object, ifName, is added to the MIB.
  This object contains the device's local name (e.g., the name used
  at the device's local console) for the interface of which the
  relevant entry in the ifTable is a component.  For example,
  consider a router having an interface composed of PPP running over
  an RS-232 port.  If the router uses the name "wan1" for the
  (combined) interface, then the ifName objects for the
  corresponding PPP and RS-232 entries in the ifTable would both
  have the value "wan1".  On the other hand, if the router uses the
  name "wan1.1" for the PPP interface and "wan1.2" for the RS-232
  port, then the ifName objects for the corresponding PPP and RS-232
  entries in the ifTable would have the values "wan1.1" and
  "wan1.2", respectively.  As an another example, consider an agent
  which responds to SNMP queries concerning an interface on some
  other (proxied) device: if such a proxied device associates a
  particular identifier with an interface, then it is appropriate to
  use this identifier as the value of the interface's ifName, since
  the local console in this case is that of the proxied device.

  In contrast, the existing ifDescr object is intended to contain a
  description of an interface, whereas another new object, ifAlias,
  provides a location in which a network management application can
  store a non-volatile interface-naming value of its own choice.
  The ifAlias object allows a network manager to give one or more
  interfaces their own unique names, irrespective of any interface-
  stack relationship.  Further, the ifAlias name is non-volatile,
  and thus an interface must retain its assigned ifAlias value
  across reboots, even if an agent chooses a new ifIndex value for
  the interface.

3.1.6.  Counter Size

  As the speed of network media increase, the minimum time in which
  a 32 bit counter will wrap decreases.  For example, a 10Mbs stream
  of back-to-back, full-size packets causes ifInOctets to wrap in
  just over 57 minutes; at 100Mbs, the minimum wrap time is 5.7
  minutes, and at 1Gbs, the minimum is 34 seconds.  Requiring that
  interfaces be polled frequently enough not to miss a counter wrap
  is increasingly problematic.





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  A rejected solution to this problem was to scale the counters; for
  example, ifInOctets could be changed to count received octets in,
  say, 1024 byte blocks.  While it would provide acceptable
  functionality at high rates of the counted-events, at low rates it
  suffers.  If there is little traffic on an interface, there might
  be a significant interval before enough of the counted-events
  occur to cause the scaled counter to be incremented.  Traffic
  would then appear to be very bursty, leading to incorrect
  conclusions of the network's performance.

  Instead, this memo adopts expanded, 64 bit, counters.  These
  counters are provided in new "high capacity" groups.  The old,
  32-bit, counters have not been deprecated.  The 64-bit counters
  are to be used only when the 32-bit counters do not provide enough
  capacity; that is, when the 32 bit counters could wrap too fast.

  For interfaces that operate at 20,000,000 (20 million) bits per
  second or less, 32-bit byte and packet counters MUST be used.  For
  interfaces that operate faster than 20,000,000 bits/second, and
  slower than 650,000,000 bits/second, 32-bit packet counters MUST
  be used and 64-bit octet counters MUST be used.  For interfaces
  that operate at 650,000,000 bits/second or faster, 64-bit packet
  counters AND 64-bit octet counters MUST be used.

  These speed thresholds were chosen as reasonable compromises based
  on the following:

  (1)  The cost of maintaining 64-bit counters is relatively high,
       so minimizing the number of agents which must support them is
       desirable.  Common interfaces (such as 10Mbs Ethernet) should
       not require them.

  (2)  64-bit counters are a new feature, introduced in SNMPv2.  It
       is reasonable to expect that support for them will be spotty
       for the immediate future.  Thus, we wish to limit them to as
       few systems as possible.  This, in effect, means that 64-bit
       counters should be limited to higher speed interfaces.
       Ethernet (10,000,000 bps) and Token Ring (16,000,000 bps) are
       fairly wide-spread so it seems reasonable to not require 64-
       bit counters for these interfaces.

  (3)  The 32-bit octet counters will wrap in the following times,
       for the following interfaces (when transmitting maximum-sized
       packets back-to-back):

       -   10Mbs Ethernet: 57 minutes,

       -   16Mbs Token Ring: 36 minutes,



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       -   a US T3 line (45 megabits): 12 minutes,

       -   FDDI: 5.7 minutes

  (4)  The 32-bit packet counters wrap in about 57 minutes when 64-
       byte packets are transmitted back-to-back on a 650,000,000
       bit/second link.

  As an aside, a 1-terabit/second (1,000 Gbs) link will cause a 64 bit
  octet counter to wrap in just under 5 years.  Conversely, an
  81,000,000 terabit/second link is required to cause a 64-bit counter
  to wrap in 30 minutes.  We believe that, while technology rapidly
  marches forward, this link speed will not be achieved for at least
  several years, leaving sufficient time to evaluate the introduction
  of 96 bit counters.

  When 64-bit counters are in use, the 32-bit counters MUST still be
  available.  They will report the low 32-bits of the associated 64-bit
  count (e.g., ifInOctets will report the least significant 32 bits of
  ifHCInOctets).  This enhances inter-operability with existing
  implementations at a very minimal cost to agents.

  The new "high capacity" groups are:

  (1)  the ifHCFixedLengthGroup for character-oriented/fixed-length
       interfaces, and the ifHCPacketGroup for packet-based interfaces;
       both of these groups include 64 bit counters for octets, and

  (2)  the ifVHCPacketGroup for packet-based interfaces; this group
       includes 64 bit counters for octets and packets.

3.1.7.  Interface Speed

  Network speeds are increasing.  The range of ifSpeed is limited to
  reporting a maximum speed of (2**31)-1 bits/second, or approximately
  2.2Gbs.  SONET defines an OC-48 interface, which is defined at
  operating at 48 times 51 Mbs, which is a speed in excess of 2.4Gbs.
  Thus, ifSpeed is insufficient for the future, and this memo defines
  an additional object: ifHighSpeed.

  The ifHighSpeed object reports the speed of the interface in
  1,000,000 (1 million) bits/second units.  Thus, the true speed of the
  interface will be the value reported by this object, plus or minus
  500,000 bits/second.







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  Other alternatives considered (but rejected) were:

  (1)  Making the interface speed a 64-bit gauge.  This was rejected
       since the current SMI does not allow such a syntax.

       Furthermore, even if 64-bit gauges were available, their use
       would require additional complexity in agents due to an
       increased requirement for 64-bit operations.

  (2)  We also considered making "high-32 bit" and "low-32-bit"
       objects which, when combined, would be a 64-bit value.  This
       simply seemed overly complex for what we are trying to do.

       Furthermore, a full 64-bits of precision does not seem
       necessary.  The value of ifHighSpeed will be the only report of
       interface speed for interfaces that are faster than
       4,294,967,295 bits per second.  At this speed, the granularity
       of ifHighSpeed will be 1,000,000 bits per second, thus the error
       will be 1/4294, or about 0.02%.  This seems reasonable.

  (3)  Adding a "scale" object, which would define the units which
       ifSpeed's value is.

       This would require two additional objects; one for the scaling
       object, and one to replace the current ifSpeed.  This later
       object is required since the semantics of ifSpeed would be
       significantly altered, and manager stations which do not
       understand the new semantics would be confused.

3.1.8.  Multicast/Broadcast Counters

  In MIB-II, the ifTable counters for multicast and broadcast packets
  are combined as counters of non-unicast packets.  In contrast, the
  ifExtensions MIB [7] defined one set of counters for multicast, and a
  separate set for broadcast packets.  With the separate counters, the
  original combined counters become redundant.  To avoid this
  redundancy, the non-unicast counters are deprecated.

  For the output broadcast and multicast counters defined in RFC 1229,
  their definitions varied slightly from the packet counters in the
  ifTable, in that they did not count errors/discarded packets.  Thus,
  this memo defines new objects with better aligned definitions.
  Counters with 64 bits of range are also needed, as explained above.








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3.1.9.  Trap Enable

  In the multi-layer interface model, each sub-layer for which there is
  an entry in the ifTable can generate linkUp/Down Traps.  Since
  interface state changes would tend to propagate through the interface
  (from top to bottom, or bottom to top), it is likely that several
  traps would be generated for each linkUp/Down occurrence.

  It is desirable to provide a mechanism for manager stations to
  control the generation of these traps.  To this end, the
  ifLinkUpDownTrapEnable object has been added.  This object allows
  managers to limit generation of traps to just the sub-layers of
  interest.

  The default setting should limit the number of traps generated to one
  per interface per linkUp/Down event.  Furthermore, it seems that the
  state changes of most interest to network managers occur at the
  lowest level of an interface stack.  Therefore we specify that by
  default, only the lowest sub-layer of the interface generate traps.

3.1.10.  Addition of New ifType values

  Over time, there is the need to add new ifType enumerated values for
  new interface types.  If the syntax of ifType were defined in the MIB
  in section 6, then a new version of this MIB would have to be re-
  issued in order to define new values.  In the past, re- issuing of a
  MIB has occurred only after several years.

  Therefore, the syntax of ifType is changed to be a textual
  convention, such that the enumerated integer values are now defined
  in the textual convention, IANAifType, defined in a different
  document.  This allows additional values to be documented without
  having to re-issue a new version of this document.  The Internet
  Assigned Number Authority (IANA) is responsible for the assignment of
  all Internet numbers, including various SNMP-related numbers, and
  specifically, new ifType values.

3.1.11.  InterfaceIndex Textual Convention

  A new textual convention, InterfaceIndex, has been defined.  This
  textual convention "contains" all of the semantics of the ifIndex
  object.  This allows other mib modules to easily import the semantics
  of ifIndex.








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3.1.12.  New states for IfOperStatus

  Three new states have been added to ifOperStatus: 'dormant',
  'notPresent', and 'lowerLayerDown'.

  The dormant state indicates that the relevant interface is not
  actually in a condition to pass packets (i.e., it is not "up") but is
  in a "pending" state, waiting for some external event.  For "on-
  demand" interfaces, this new state identifies the situation where the
  interface is waiting for events to place it in the up state.
  Examples of such events might be:

  (1)  having packets to transmit before establishing a connection
       to a remote system;

  (2)  having a remote system establish a connection to the
       interface (e.g. dialing up to a slip-server).

  The notPresent state is a refinement on the down state which
  indicates that the relevant interface is down specifically because
  some component (typically, a hardware component) is not present in
  the managed system.  Examples of use of the notPresent state are:

  (1)  to allow an interface's conceptual row including its counter
       values to be retained across a "hot swap" of a card/module,
       and/or

  (2)  to allow an interface's conceptual row to be created, and
       thereby enable interfaces to be pre-configured prior to
       installation of the hardware needed to make the interface
       operational.

  Agents are not required to support interfaces in the notPresent
  state.  However, from a conceptual viewpoint, when a row in the
  ifTable is created, it first enters the notPresent state and then
  subsequently transitions into the down state; similarly, when a row
  in the ifTable is deleted, it first enters the notPresent state and
  then subsequently the object instances are deleted.  For an agent
  with no support for notPresent, both of these transitions (from the
  notPresent state to the down state, and from the notPresent state to
  the instances being removed) are immediate, i.e., the transition does
  not last long enough to be recorded by ifOperStatus.  Even for those
  agents which do support interfaces in the notPresent state, the
  length of time and conditions under which an interface stays in the
  notPresent state is implementation-specific.






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  The lowerLayerDown state is also a refinement on the down state.
  This new state indicates that this interface runs "on top of" one or
  more other interfaces (see ifStackTable) and that this interface is
  down specifically because one or more of these lower-layer interfaces
  are down.

3.1.13.  IfAdminStatus and IfOperStatus

  The down state of ifOperStatus now has two meanings, depending on the
  value of ifAdminStatus.

  (1)  if ifAdminStatus is not down and ifOperStatus is down then a
       fault condition is presumed to exist on the interface.

  (2)  if ifAdminStatus is down, then ifOperStatus will normally
       also be down (or notPresent) i.e., there is not (necessarily) a
       fault condition on the interface.

  Note that when ifAdminStatus transitions to down, ifOperStatus will
  normally also transition to down.  In this situation, it is possible
  that ifOperStatus's transition will not occur immediately, but rather
  after a small time lag to complete certain operations before going
  "down"; for example, it might need to finish transmitting a packet.
  If a manager station finds that ifAdminStatus is down and
  ifOperStatus is not down for a particular interface, the manager
  station should wait a short while and check again.  If the condition
  still exists, only then should it raise an error indication.
  Naturally, it should also ensure that ifLastChange has not changed
  during this interval.

  Whenever an interface table entry is created (usually as a result of
  system initialization), the relevant instance of ifAdminStatus is set
  to down, and presumably ifOperStatus will be down or notPresent.

  An interface may be enabled in two ways: either as a result of
  explicit management action (e.g. setting ifAdminStatus to up) or as a
  result of the managed system's initialization process.  When
  ifAdminStatus changes to the up state, the related ifOperStatus
  should do one of the following:

  (1)  Change to the up state if and only if the interface is able
       to send and receive packets.

  (2)  Change to the lowerLayerDown state if and only if the
       interface is prevented from entering the up state because of the
       state of one or more of the interfaces beneath it in the
       interface stack.




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  (3)  Change to the dormant state if and only if the interface is
       found to be operable, but the interface is waiting for other,
       external, events to occur before it can transmit or receive
       packets.  Presumably when the expected events occur, the
       interface will then change to the up state.

  (4)  Remain in the down state if an error or other fault condition
       is detected on the interface.

  (5)  Change to the unknown state if, for some reason, the state of
       the interface can not be ascertained.

  (6)  Change to the testing state if some test(s) must be performed
       on the interface. Presumably after completion of the test, the
       interface's state will change to up, dormant, or down, as
       appropriate.

  (7)  Remain in the notPresent state if interface components are
       missing.

3.1.14.  IfOperStatus in an Interface Stack

  When an interface is a part of an interface-stack, but is not the
  lowest interface in the stack, then:

  (1)  ifOperStatus has the value 'up' if it is able to pass packets
       due to one or more interfaces below it in the stack being 'up',
       irrespective of whether other interfaces below it are 'down',
       'dormant', 'notPresent', 'lowerLayerDown', 'unknown' or
       'testing'.

  (2)  ifOperStatus may have the value 'up' or 'dormant' if one or
       more interfaces below it in the stack are 'dormant', and all
       others below it are either 'down', 'dormant', 'notPresent',
       'lowerLayerDown', 'unknown' or 'testing'.

  (3)  ifOperStatus has the value 'lowerLayerDown' while all
       interfaces below it in the stack are either 'down',
       'notPresent', 'lowerLayerDown', or 'testing'.

3.1.15.  Traps

  The exact definition of when linkUp and linkDown traps are generated
  has been changed to reflect the changes to ifAdminStatus and
  ifOperStatus.






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  Operational experience indicates that management stations are most
  concerned with an interface being in the down state and the fact that
  this state may indicate a failure.  Thus, it is most useful to
  instrument transitions into/out of either the up state or the down
  state.

  Instrumenting transitions into or out of the up state was rejected
  since it would have the drawback that a demand interface might have
  many transitions between up and dormant, leading to many linkUp traps
  and no linkDown traps.  Furthermore, if a node's only interface is
  the demand interface, then a transition to dormant would entail
  generation of a linkDown trap, necessitating bringing the link to the
  up state (and a linkUp trap)!!

  On the other hand, instrumenting transitions into or out of the down
  state (to/from all other states except notPresent) has the
  advantages:

  (1)  A transition into the down state (from a state other than
       notPresent) will occur when an error is detected on an
       interface.  Error conditions are presumably of great interest to
       network managers.

  (2)  Departing the down state (to a state other than the
       notPresent state) generally indicates that the interface is
       going to either up or dormant, both of which are considered
       "healthy" states.

  Furthermore, it is believed that generating traps on transitions into
  or out of the down state (except to/from the notPresent state) is
  generally consistent with current usage and interpretation of these
  traps by manager stations.

  Transitions to/from the notPresent state are concerned with the
  insertion and removal of hardware, and are outside the scope of these
  traps.

  Therefore, this memo defines that LinkUp and linkDown traps are
  generated on just after ifOperStatus leaves, or just before it
  enters, the down state, respectively; except that LinkUp and linkDown
  traps never generated on transitions to/from the notPresent state.

  Note that this definition allows a node with only one interface to
  transmit a linkDown trap before that interface goes down.  (Of
  course, when the interface is going down because of a failure
  condition, the linkDown trap probably cannot be successfully
  transmitted anyway.)




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  Some interfaces perform a link "training" function when trying to
  bring the interface up.  In the event that such an interface were
  defective, then the training function would fail and the interface
  would remain down, and the training function might be repeated at
  appropriate intervals.  If the interface, while performing this
  training function, were considered to the in the testing state, then
  linkUp and linkDown traps would be generated for each start and end
  of the training function.  This is not the intent of the linkUp and
  linkDown traps, and therefore, while performing such a training
  function, the interface's state should be represented as down.

  An exception to the above generation of linkUp/linkDown traps on
  changes in ifOperStatus, occurs when an interface is "flapping",
  i.e., when it is rapidly oscillating between the up and down states.
  If traps were generated for each such oscillation, the network and
  the network management system would be flooded with unnecessary
  traps.  In such a situation, the agent should rate- limit its
  generation of traps.

3.1.16.  ifSpecific

  The original definition of the OBJECT IDENTIFIER value of ifSpecific
  was not sufficiently clear.  As a result, different implementors used
  it differently, and confusion resulted.  Some implementations set the
  value of ifSpecific to the OBJECT IDENTIFIER that defines the media-
  specific MIB, i.e., the "foo" of:

             foo OBJECT IDENTIFIER ::= { transmission xxx }

  while others set it to be OBJECT IDENTIFIER of the specific table or
  entry in the appropriate media-specific MIB (i.e., fooTable or
  fooEntry), while still others set it be the OBJECT IDENTIFIER of the
  index object of the table's row, including instance identifier,
  (i.e., fooIfIndex.ifIndex).  A definition based on the latter would
  not be sufficient unless it also allowed for media- specific MIBs
  which include several tables, where each table has its own
  (different) indexing.

  The only definition that can both be made explicit and can cover all
  the useful situations is to have ifSpecific be the most general value
  for the media-specific MIB module (the first example given above).
  This effectively makes it redundant because it contains no more
  information than is provided by ifType.  Thus, ifSpecific has been
  deprecated.







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3.1.17.  Creation/Deletion of Interfaces

  While some interfaces, for example, most physical interfaces, cannot
  be created via network management, other interfaces such as logical
  interfaces sometimes can be.  The ifTable contains only generic
  information about an interface.  Almost all 'create-able' interfaces
  have other, media-specific, information through which configuration
  parameters may be supplied prior to creating such an interface.
  Thus, the ifTable does not itself support the creation or deletion of
  an interface (specifically, it has no RowStatus [2] column).  Rather,
  if a particular interface type supports the dynamic creation and/or
  deletion of an interface of that type, then that media-specific MIB
  should include an appropriate RowStatus object (see the ATM LAN-
  Emulation Client MIB [8] for an example of a MIB which does this).
  Typically, when such a RowStatus object is created/deleted, then the
  conceptual row in the ifTable appears/disappears as a by-product, and
  an ifIndex value (chosen by the agent) is stored in an appropriate
  object in the media-specific MIB.

3.1.18.  All Values Must be Known

  There are a number of situations where an agent does not know the
  value of one or more objects for a particular interface.  In all such
  circumstances, an agent MUST NOT instantiate an object with an
  incorrect value; rather, it MUST respond with the appropriate
  error/exception condition (e.g., noSuchInstance for SNMPv2).

  One example is where an agent is unable to count the occurrences
  defined by one (or more) of the ifTable counters.  In this
  circumstance, the agent MUST NOT instantiate the particular counter
  with a value of, say, zero.  To do so would be to provide mis-
  information to a network management application reading the zero
  value, and thereby assuming that there have been no occurrences of
  the event (e.g., no input errors because ifInErrors is always zero).

  Sometimes the lack of knowledge of an object's value is temporary.
  For example, when the MTU of an interface is a configured value and a
  device dynamically learns the configured value through (after)
  exchanging messages over the interface (e.g., ATM LAN- Emulation
  [8]).  In such a case, the value is not known until after the ifTable
  entry has already been created.  In such a case, the ifTable entry
  should be created without an instance of the object whose value is
  unknown; later, when the value becomes known, the missing object can
  then be instantiated (e.g., the instance of ifMtu is only
  instantiated once the interface's MTU becomes known).






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  As a result of this "known values" rule, management applications MUST
  be able to cope with the responses to retrieving the object instances
  within a conceptual row of the ifTable revealing that some of the
  row's columnar objects are missing/not available.

4.  Media-Specific MIB Applicability

  The exact use and semantics of many objects in this MIB are open to
  some interpretation.  This is a result of the generic nature of this
  MIB.  It is not always possible to come up with specific,
  unambiguous, text that covers all cases and yet preserves the generic
  nature of the MIB.

  Therefore, it is incumbent upon a media-specific MIB designer to,
  wherever necessary, clarify the use of the objects in this MIB with
  respect to the media-specific MIB.

  Specific areas of clarification include

  Layering Model
       The media-specific MIB designer MUST completely and
       unambiguously specify the layering model used.  Each individual
       sub-layer must be identified, as must the ifStackTable's
       portrayal of the relationship(s) between the sub-layers.

  Virtual Circuits
       The media-specific MIB designer MUST specify whether virtual
       circuits are assigned entries in the ifTable or not.  If they
       are, compelling rationale must be presented.

  ifRcvAddressTable
       The media-specific MIB designer MUST specify the applicability
       of the ifRcvAddressTable.

  ifType
       For each of the ifType values to which the media-specific MIB
       applies, it must specify the mapping of ifType values to media-
       specific MIB module(s) and instances of MIB objects within those
       modules.

  However, wherever this interface MIB is specific in the semantics,
  DESCRIPTION, or applicability of objects, the media-specific MIB
  designer MUST NOT change said semantics, DESCRIPTION, or
  applicability.







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5.  Overview

  This MIB consists of 4 tables:

  ifTable
       This table is the ifTable from MIB-II.

       ifXTable
       This table contains objects that have been added to the
       Interface MIB as a result of the Interface Evolution effort, or
       replacements for objects of the original (MIB-II) ifTable that
       were deprecated because the semantics of said objects have
       significantly changed.  This table also contains objects that
       were previously in the ifExtnsTable.

  ifStackTable
       This table contains objects that define the relationships among
       the sub-layers of an interface.

  ifRcvAddressTable
       This table contains objects that are used to define the media-
       level addresses which this interface will receive.  This table
       is a generic table.  The designers of media- specific MIBs must
       define exactly how this table applies to their specific MIB.

6.  Interfaces Group Definitions

  IF-MIB DEFINITIONS ::= BEGIN

  IMPORTS
      MODULE-IDENTITY, OBJECT-TYPE, Counter32, Gauge32, Counter64,
      Integer32, TimeTicks, mib-2,
      NOTIFICATION-TYPE                        FROM SNMPv2-SMI
      TEXTUAL-CONVENTION, DisplayString,
      PhysAddress, TruthValue, RowStatus,
      TimeStamp, AutonomousType, TestAndIncr   FROM SNMPv2-TC
      MODULE-COMPLIANCE, OBJECT-GROUP          FROM SNMPv2-CONF
      snmpTraps                                FROM SNMPv2-MIB
      IANAifType                               FROM IANAifType-MIB;












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  ifMIB MODULE-IDENTITY
      LAST-UPDATED "9611031355Z"
      ORGANIZATION "IETF Interfaces MIB Working Group"
      CONTACT-INFO
              "   Keith McCloghrie
                  Cisco Systems, Inc.
                  170 West Tasman Drive
                  San Jose, CA  95134-1706
                  US

                  408-526-5260
                  [email protected]"
      DESCRIPTION
              "The MIB module to describe generic objects for
              network interface sub-layers.  This MIB is an updated
              version of MIB-II's ifTable, and incorporates the
              extensions defined in RFC 1229."
      REVISION      "9602282155Z"
      DESCRIPTION
              "Revisions made by the Interfaces MIB WG."
      REVISION      "9311082155Z"
      DESCRIPTION
              "Initial revision, published as part of RFC 1573."
      ::= { mib-2 31 }


  ifMIBObjects OBJECT IDENTIFIER ::= { ifMIB 1 }

  interfaces   OBJECT IDENTIFIER ::= { mib-2 2 }


  OwnerString ::= TEXTUAL-CONVENTION
      DISPLAY-HINT "255a"
      STATUS       current
      DESCRIPTION
              "This data type is used to model an administratively
              assigned name of the owner of a resource.  This
              information is taken from the NVT ASCII character set.
              It is suggested that this name contain one or more of
              the following: ASCII form of the manager station's
              transport address, management station name (e.g.,
              domain name), network management personnel's name,
              location, or phone number.  In some cases the agent
              itself will be the owner of an entry.  In these cases,
              this string shall be set to a string starting with
              'agent'."
      SYNTAX       OCTET STRING (SIZE(0..255))




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  -- InterfaceIndex contains the semantics of ifIndex and
  -- should be used for any objects defined on other mib
  -- modules that need these semantics.

  InterfaceIndex ::= TEXTUAL-CONVENTION
      DISPLAY-HINT "d"
      STATUS       current
      DESCRIPTION
              "A unique value, greater than zero, for each interface
              or interface sub-layer in the managed system.  It is
              recommended that values are assigned contiguously
              starting from 1.  The value for each interface sub-
              layer must remain constant at least from one re-
              initialization of the entity's network management
              system to the next re-initialization."
      SYNTAX       Integer32 (1..2147483647)


  InterfaceIndexOrZero ::= TEXTUAL-CONVENTION
      DISPLAY-HINT "d"
      STATUS       current
      DESCRIPTION
              "This textual convention is an extension of the
              InterfaceIndex convention.  The latter defines a
              greater than zero value used to identify an interface
              or interface sub-layer in the managed system.  This
              extension permits the additional value of zero.  the
              value zero is object-specific and must therefore be
              defined as part of the description of any object which
              uses this syntax.  Examples of the usage of zero might
              include situations where interface was unknown, or
              when none or all interfaces need to be referenced."
      SYNTAX       Integer32 (0..2147483647)


  ifNumber  OBJECT-TYPE
      SYNTAX      Integer32
      MAX-ACCESS  read-only
      STATUS      current
      DESCRIPTION
              "The number of network interfaces (regardless of their
              current state) present on this system."
      ::= { interfaces 1 }








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  ifTableLastChange  OBJECT-TYPE
      SYNTAX      TimeTicks
      MAX-ACCESS  read-only
      STATUS      current
      DESCRIPTION
              "The value of sysUpTime at the time of the last
              creation or deletion of an entry in the ifTable.  If
              the number of entries has been unchanged since the
              last re-initialization of the local network management
              subsystem, then this object contains a zero value."
      ::= { ifMIBObjects 5 }


  -- the Interfaces table

  -- The Interfaces table contains information on the entity's
  -- interfaces.  Each sub-layer below the internetwork-layer
  -- of a network interface is considered to be an interface.

  ifTable OBJECT-TYPE
      SYNTAX      SEQUENCE OF IfEntry
      MAX-ACCESS  not-accessible
      STATUS      current
      DESCRIPTION
              "A list of interface entries.  The number of entries
              is given by the value of ifNumber."
      ::= { interfaces 2 }

  ifEntry OBJECT-TYPE
      SYNTAX      IfEntry
      MAX-ACCESS  not-accessible
      STATUS      current
      DESCRIPTION
              "An entry containing management information applicable
              to a particular interface."
      INDEX   { ifIndex }



      ::= { ifTable 1 }

  IfEntry ::=
      SEQUENCE {
          ifIndex                 InterfaceIndex,
          ifDescr                 DisplayString,
          ifType                  IANAifType,
          ifMtu                   Integer32,
          ifSpeed                 Gauge32,



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          ifPhysAddress           PhysAddress,
          ifAdminStatus           INTEGER,
          ifOperStatus            INTEGER,
          ifLastChange            TimeTicks,
          ifInOctets              Counter32,
          ifInUcastPkts           Counter32,
          ifInNUcastPkts          Counter32,  -- deprecated
          ifInDiscards            Counter32,
          ifInErrors              Counter32,
          ifInUnknownProtos       Counter32,
          ifOutOctets             Counter32,
          ifOutUcastPkts          Counter32,
          ifOutNUcastPkts         Counter32,  -- deprecated
          ifOutDiscards           Counter32,
          ifOutErrors             Counter32,
          ifOutQLen               Gauge32,    -- deprecated
          ifSpecific              OBJECT IDENTIFIER -- deprecated
      }


  ifIndex OBJECT-TYPE
      SYNTAX      InterfaceIndex
      MAX-ACCESS  read-only
      STATUS      current
      DESCRIPTION
              "A unique value, greater than zero, for each
              interface.  It is recommended that values are assigned
              contiguously starting from 1.  The value for each
              interface sub-layer must remain constant at least from
              one re-initialization of the entity's network
              management system to the next re-initialization."
      ::= { ifEntry 1 }

  ifDescr OBJECT-TYPE
      SYNTAX      DisplayString (SIZE (0..255))
      MAX-ACCESS  read-only


      STATUS      current
      DESCRIPTION
              "A textual string containing information about the
              interface.  This string should include the name of the
              manufacturer, the product name and the version of the
              interface hardware/software."
      ::= { ifEntry 2 }






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  ifType OBJECT-TYPE
      SYNTAX      IANAifType
      MAX-ACCESS  read-only
      STATUS      current
      DESCRIPTION
              "The type of interface.  Additional values for ifType
              are assigned by the Internet Assigned Numbers
              Authority (IANA), through updating the syntax of the
              IANAifType textual convention."
      ::= { ifEntry 3 }

  ifMtu OBJECT-TYPE
      SYNTAX      Integer32
      MAX-ACCESS  read-only
      STATUS      current
      DESCRIPTION
              "The size of the largest packet which can be
              sent/received on the interface, specified in octets.
              For interfaces that are used for transmitting network
              datagrams, this is the size of the largest network
              datagram that can be sent on the interface."
      ::= { ifEntry 4 }

  ifSpeed OBJECT-TYPE
      SYNTAX      Gauge32
      MAX-ACCESS  read-only
      STATUS      current
      DESCRIPTION
              "An estimate of the interface's current bandwidth in
              bits per second.  For interfaces which do not vary in
              bandwidth or for those where no accurate estimation
              can be made, this object should contain the nominal
              bandwidth.  If the bandwidth of the interface is
              greater than the maximum value reportable by this
              object then this object should report its maximum
              value (4,294,967,295) and ifHighSpeed must be used to
              report the interace's speed.  For a sub-layer which
              has no concept of bandwidth, this object should be
              zero."
      ::= { ifEntry 5 }

  ifPhysAddress OBJECT-TYPE
      SYNTAX      PhysAddress
      MAX-ACCESS  read-only
      STATUS      current






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      DESCRIPTION
              "The interface's address at its protocol sub-layer.
              For example, for an 802.x interface, this object
              normally contains a MAC address.  The interface's
              media-specific MIB must define the bit and byte
              ordering and the format of the value of this object.
              For interfaces which do not have such an address
              (e.g., a serial line), this object should contain an
              octet string of zero length."
      ::= { ifEntry 6 }

  ifAdminStatus OBJECT-TYPE
      SYNTAX  INTEGER {
                  up(1),       -- ready to pass packets
                  down(2),
                  testing(3)   -- in some test mode
              }
      MAX-ACCESS  read-write
      STATUS      current
      DESCRIPTION
              "The desired state of the interface.  The testing(3)
              state indicates that no operational packets can be
              passed.  When a managed system initializes, all
              interfaces start with ifAdminStatus in the down(2)
              state.  As a result of either explicit management
              action or per configuration information retained by
              the managed system, ifAdminStatus is then changed to
              either the up(1) or testing(3) states (or remains in
              the down(2) state)."
      ::= { ifEntry 7 }

  ifOperStatus OBJECT-TYPE
      SYNTAX  INTEGER {
                  up(1),        -- ready to pass packets
                  down(2),
                  testing(3),   -- in some test mode
                  unknown(4),   -- status can not be determined
                                -- for some reason.
                  dormant(5),
                  notPresent(6),    -- some component is missing
                  lowerLayerDown(7) -- down due to state of
                                    -- lower-layer interface(s)
              }








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      MAX-ACCESS  read-only
      STATUS      current
      DESCRIPTION
              "The current operational state of the interface.  The
              testing(3) state indicates that no operational packets
              can be passed.  If ifAdminStatus is down(2) then
              ifOperStatus should be down(2).  If ifAdminStatus is
              changed to up(1) then ifOperStatus should change to
              up(1) if the interface is ready to transmit and
              receive network traffic; it should change to
              dormant(5) if the interface is waiting for external
              actions (such as a serial line waiting for an incoming
              connection); it should remain in the down(2) state if
              and only if there is a fault that prevents it from
              going to the up(1) state; it should remain in the
              notPresent(6) state if the interface has missing
              (typically, hardware) components."
      ::= { ifEntry 8 }

  ifLastChange OBJECT-TYPE
      SYNTAX      TimeTicks
      MAX-ACCESS  read-only
      STATUS      current
      DESCRIPTION
              "The value of sysUpTime at the time the interface
              entered its current operational state.  If the current
              state was entered prior to the last re-initialization
              of the local network management subsystem, then this
              object contains a zero value."
      ::= { ifEntry 9 }

  ifInOctets OBJECT-TYPE
      SYNTAX      Counter32
      MAX-ACCESS  read-only
      STATUS      current
      DESCRIPTION
              "The total number of octets received on the interface,
              including framing characters.

              Discontinuities in the value of this counter can occur
              at re-initialization of the management system, and at
              other times as indicated by the value of
              ifCounterDiscontinuityTime."
      ::= { ifEntry 10 }







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  ifInUcastPkts OBJECT-TYPE
      SYNTAX      Counter32
      MAX-ACCESS  read-only
      STATUS      current
      DESCRIPTION
              "The number of packets, delivered by this sub-layer to
              a higher (sub-)layer, which were not addressed to a
              multicast or broadcast address at this sub-layer.

              Discontinuities in the value of this counter can occur
              at re-initialization of the management system, and at
              other times as indicated by the value of
              ifCounterDiscontinuityTime."
      ::= { ifEntry 11 }

  ifInNUcastPkts OBJECT-TYPE
      SYNTAX  Counter32
      MAX-ACCESS  read-only
      STATUS      deprecated
      DESCRIPTION
              "The number of packets, delivered by this sub-layer to
              a higher (sub-)layer, which were addressed to a
              multicast or broadcast address at this sub-layer.

              Discontinuities in the value of this counter can occur
              at re-initialization of the management system, and at
              other times as indicated by the value of
              ifCounterDiscontinuityTime.

              This object is deprecated in favour of
              ifInMulticastPkts and ifInBroadcastPkts."
      ::= { ifEntry 12 }

  ifInDiscards OBJECT-TYPE
      SYNTAX      Counter32
      MAX-ACCESS  read-only
      STATUS      current
      DESCRIPTION
              "The number of inbound packets which were chosen to be
              discarded even though no errors had been detected to
              prevent their being deliverable to a higher-layer
              protocol.  One possible reason for discarding such a
              packet could be to free up buffer space.

              Discontinuities in the value of this counter can occur
              at re-initialization of the management system, and at
              other times as indicated by the value of
              ifCounterDiscontinuityTime."



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      ::= { ifEntry 13 }

  ifInErrors OBJECT-TYPE
      SYNTAX      Counter32
      MAX-ACCESS  read-only
      STATUS      current
      DESCRIPTION
              "For packet-oriented interfaces, the number of inbound
              packets that contained errors preventing them from
              being deliverable to a higher-layer protocol.  For
              character-oriented or fixed-length interfaces, the
              number of inbound transmission units that contained
              errors preventing them from being deliverable to a
              higher-layer protocol.

              Discontinuities in the value of this counter can occur
              at re-initialization of the management system, and at
              other times as indicated by the value of
              ifCounterDiscontinuityTime."
      ::= { ifEntry 14 }

  ifInUnknownProtos OBJECT-TYPE
      SYNTAX      Counter32
      MAX-ACCESS  read-only
      STATUS      current
      DESCRIPTION
              "For packet-oriented interfaces, the number of packets
              received via the interface which were discarded
              because of an unknown or unsupported protocol.  For
              character-oriented or fixed-length interfaces that
              support protocol multiplexing the number of
              transmission units received via the interface which
              were discarded because of an unknown or unsupported
              protocol.  For any interface that does not support
              protocol multiplexing, this counter will always be 0.

              Discontinuities in the value of this counter can occur
              at re-initialization of the management system, and at
              other times as indicated by the value of
              ifCounterDiscontinuityTime."
      ::= { ifEntry 15 }










McCloghrie & Kastenholz     Standards Track                    [Page 35]

RFC 2233            Interfaces Group MIB using SMIv2       November 1997


  ifOutOctets OBJECT-TYPE
      SYNTAX      Counter32
      MAX-ACCESS  read-only
      STATUS      current
      DESCRIPTION
              "The total number of octets transmitted out of the
              interface, including framing characters.

              Discontinuities in the value of this counter can occur
              at re-initialization of the management system, and at
              other times as indicated by the value of
              ifCounterDiscontinuityTime."
      ::= { ifEntry 16 }

  ifOutUcastPkts OBJECT-TYPE
      SYNTAX      Counter32
      MAX-ACCESS  read-only
      STATUS      current
      DESCRIPTION
              "The total number of packets that higher-level
              protocols requested be transmitted, and which were not
              addressed to a multicast or broadcast address at this
              sub-layer, including those that were discarded or not
              sent.

              Discontinuities in the value of this counter can occur
              at re-initialization of the management system, and at
              other times as indicated by the value of
              ifCounterDiscontinuityTime."
      ::= { ifEntry 17 }

  ifOutNUcastPkts OBJECT-TYPE
      SYNTAX      Counter32
      MAX-ACCESS  read-only
      STATUS      deprecated
      DESCRIPTION
              "The total number of packets that higher-level
              protocols requested be transmitted, and which were
              addressed to a multicast or broadcast address at this
              sub-layer, including those that were discarded or not
              sent.

              Discontinuities in the value of this counter can occur
              at re-initialization of the management system, and at
              other times as indicated by the value of
              ifCounterDiscontinuityTime.





McCloghrie & Kastenholz     Standards Track                    [Page 36]

RFC 2233            Interfaces Group MIB using SMIv2       November 1997


              This object is deprecated in favour of
              ifOutMulticastPkts and ifOutBroadcastPkts."
      ::= { ifEntry 18 }

  ifOutDiscards OBJECT-TYPE
      SYNTAX      Counter32
      MAX-ACCESS  read-only
      STATUS      current
      DESCRIPTION
              "The number of outbound packets which were chosen to
              be discarded even though no errors had been detected
              to prevent their being transmitted.  One possible
              reason for discarding such a packet could be to free
              up buffer space.

              Discontinuities in the value of this counter can occur
              at re-initialization of the management system, and at
              other times as indicated by the value of
              ifCounterDiscontinuityTime."
      ::= { ifEntry 19 }

  ifOutErrors OBJECT-TYPE
      SYNTAX      Counter32
      MAX-ACCESS  read-only
      STATUS      current
      DESCRIPTION
              "For packet-oriented interfaces, the number of
              outbound packets that could not be transmitted because
              of errors.  For character-oriented or fixed-length
              interfaces, the number of outbound transmission units
              that could not be transmitted because of errors.

              Discontinuities in the value of this counter can occur
              at re-initialization of the management system, and at
              other times as indicated by the value of
              ifCounterDiscontinuityTime."
      ::= { ifEntry 20 }


  ifOutQLen OBJECT-TYPE
      SYNTAX      Gauge32
      MAX-ACCESS  read-only
      STATUS      deprecated
      DESCRIPTION
              "The length of the output packet queue (in packets)."
      ::= { ifEntry 21 }





McCloghrie & Kastenholz     Standards Track                    [Page 37]

RFC 2233            Interfaces Group MIB using SMIv2       November 1997


  ifSpecific OBJECT-TYPE
      SYNTAX      OBJECT IDENTIFIER
      MAX-ACCESS  read-only
      STATUS      deprecated
      DESCRIPTION
              "A reference to MIB definitions specific to the
              particular media being used to realize the interface.
              It is recommended that this value point to an instance
              of a MIB object in the media-specific MIB, i.e., that
              this object have the semantics associated with the
              InstancePointer textual convention defined in RFC
              1903.  In fact, it is recommended that the media-
              specific MIB specify what value ifSpecific should/can
              take for values of ifType.  If no MIB definitions
              specific to the particular media are available, the
              value should be set to the OBJECT IDENTIFIER { 0 0 }."
      ::= { ifEntry 22 }



  --
  --   Extension to the interface table
  --
  -- This table replaces the ifExtnsTable table.
  --

  ifXTable        OBJECT-TYPE
      SYNTAX      SEQUENCE OF IfXEntry
      MAX-ACCESS  not-accessible
      STATUS      current
      DESCRIPTION
              "A list of interface entries.  The number of entries
              is given by the value of ifNumber.  This table
              contains additional objects for the interface table."
      ::= { ifMIBObjects 1 }

  ifXEntry        OBJECT-TYPE
      SYNTAX      IfXEntry
      MAX-ACCESS  not-accessible
      STATUS      current
      DESCRIPTION
              "An entry containing additional management information
              applicable to a particular interface."
      AUGMENTS    { ifEntry }
      ::= { ifXTable 1 }






McCloghrie & Kastenholz     Standards Track                    [Page 38]

RFC 2233            Interfaces Group MIB using SMIv2       November 1997


  IfXEntry ::=
      SEQUENCE {
          ifName                  DisplayString,
          ifInMulticastPkts       Counter32,
          ifInBroadcastPkts       Counter32,
          ifOutMulticastPkts      Counter32,
          ifOutBroadcastPkts      Counter32,
          ifHCInOctets            Counter64,
          ifHCInUcastPkts         Counter64,
          ifHCInMulticastPkts     Counter64,
          ifHCInBroadcastPkts     Counter64,
          ifHCOutOctets           Counter64,
          ifHCOutUcastPkts        Counter64,
          ifHCOutMulticastPkts    Counter64,
          ifHCOutBroadcastPkts    Counter64,
          ifLinkUpDownTrapEnable  INTEGER,
          ifHighSpeed             Gauge32,
          ifPromiscuousMode       TruthValue,
          ifConnectorPresent      TruthValue,
          ifAlias                 DisplayString,
          ifCounterDiscontinuityTime TimeStamp
      }


  ifName OBJECT-TYPE
      SYNTAX      DisplayString
      MAX-ACCESS  read-only
      STATUS      current
      DESCRIPTION
              "The textual name of the interface.  The value of this
              object should be the name of the interface as assigned
              by the local device and should be suitable for use in
              commands entered at the device's `console'.  This
              might be a text name, such as `le0' or a simple port
              number, such as `1', depending on the interface naming
              syntax of the device.  If several entries in the
              ifTable together represent a single interface as named
              by the device, then each will have the same value of
              ifName.  Note that for an agent which responds to SNMP
              queries concerning an interface on some other
              (proxied) device, then the value of ifName for such an
              interface is the proxied device's local name for it.

              If there is no local name, or this object is otherwise
              not applicable, then this object contains a zero-
              length string."
      ::= { ifXEntry 1 }




McCloghrie & Kastenholz     Standards Track                    [Page 39]

RFC 2233            Interfaces Group MIB using SMIv2       November 1997


  ifInMulticastPkts OBJECT-TYPE
      SYNTAX      Counter32
      MAX-ACCESS  read-only
      STATUS      current
      DESCRIPTION
              "The number of packets, delivered by this sub-layer to
              a higher (sub-)layer, which were addressed to a
              multicast address at this sub-layer.  For a MAC layer
              protocol, this includes both Group and Functional
              addresses.

              Discontinuities in the value of this counter can occur
              at re-initialization of the management system, and at
              other times as indicated by the value of
              ifCounterDiscontinuityTime."
      ::= { ifXEntry 2 }

  ifInBroadcastPkts OBJECT-TYPE
      SYNTAX      Counter32
      MAX-ACCESS  read-only
      STATUS      current
      DESCRIPTION
              "The number of packets, delivered by this sub-layer to
              a higher (sub-)layer, which were addressed to a
              broadcast address at this sub-layer.

              Discontinuities in the value of this counter can occur
              at re-initialization of the management system, and at
              other times as indicated by the value of
              ifCounterDiscontinuityTime."
      ::= { ifXEntry 3 }

  ifOutMulticastPkts OBJECT-TYPE
      SYNTAX      Counter32
      MAX-ACCESS  read-only
      STATUS      current
      DESCRIPTION
              "The total number of packets that higher-level
              protocols requested be transmitted, and which were
              addressed to a multicast address at this sub-layer,
              including those that were discarded or not sent.  For
              a MAC layer protocol, this includes both Group and
              Functional addresses.

              Discontinuities in the value of this counter can occur
              at re-initialization of the management system, and at
              other times as indicated by the value of
              ifCounterDiscontinuityTime."



McCloghrie & Kastenholz     Standards Track                    [Page 40]

RFC 2233            Interfaces Group MIB using SMIv2       November 1997


      ::= { ifXEntry 4 }

  ifOutBroadcastPkts OBJECT-TYPE
      SYNTAX      Counter32
      MAX-ACCESS  read-only
      STATUS      current
      DESCRIPTION
              "The total number of packets that higher-level
              protocols requested be transmitted, and which were
              addressed to a broadcast address at this sub-layer,
              including those that were discarded or not sent.

              Discontinuities in the value of this counter can occur
              at re-initialization of the management system, and at
              other times as indicated by the value of
              ifCounterDiscontinuityTime."
      ::= { ifXEntry 5 }

  --
  -- High Capacity Counter objects.  These objects are all
  -- 64 bit versions of the "basic" ifTable counters.  These
  -- objects all have the same basic semantics as their 32-bit
  -- counterparts, however, their syntax has been extended
  -- to 64 bits.
  --

  ifHCInOctets OBJECT-TYPE
      SYNTAX      Counter64
      MAX-ACCESS  read-only
      STATUS      current

      DESCRIPTION
              "The total number of octets received on the interface,
              including framing characters.  This object is a 64-bit
              version of ifInOctets.

              Discontinuities in the value of this counter can occur
              at re-initialization of the management system, and at
              other times as indicated by the value of
              ifCounterDiscontinuityTime."
      ::= { ifXEntry 6 }










McCloghrie & Kastenholz     Standards Track                    [Page 41]

RFC 2233            Interfaces Group MIB using SMIv2       November 1997


  ifHCInUcastPkts OBJECT-TYPE
      SYNTAX      Counter64
      MAX-ACCESS  read-only
      STATUS      current
      DESCRIPTION
              "The number of packets, delivered by this sub-layer to
              a higher (sub-)layer, which were not addressed to a
              multicast or broadcast address at this sub-layer.
              This object is a 64-bit version of ifInUcastPkts.

              Discontinuities in the value of this counter can occur
              at re-initialization of the management system, and at
              other times as indicated by the value of
              ifCounterDiscontinuityTime."
      ::= { ifXEntry 7 }

  ifHCInMulticastPkts OBJECT-TYPE
      SYNTAX      Counter64
      MAX-ACCESS  read-only
      STATUS      current
      DESCRIPTION
              "The number of packets, delivered by this sub-layer to
              a higher (sub-)layer, which were addressed to a
              multicast address at this sub-layer.  For a MAC layer
              protocol, this includes both Group and Functional
              addresses.  This object is a 64-bit version of
              ifInMulticastPkts.

              Discontinuities in the value of this counter can occur
              at re-initialization of the management system, and at
              other times as indicated by the value of
              ifCounterDiscontinuityTime."
      ::= { ifXEntry 8 }


  ifHCInBroadcastPkts OBJECT-TYPE
      SYNTAX      Counter64
      MAX-ACCESS  read-only
      STATUS      current
      DESCRIPTION
              "The number of packets, delivered by this sub-layer to
              a higher (sub-)layer, which were addressed to a
              broadcast address at this sub-layer.  This object is a
              64-bit version of ifInBroadcastPkts.

              Discontinuities in the value of this counter can occur
              at re-initialization of the management system, and at
              other times as indicated by the value of



McCloghrie & Kastenholz     Standards Track                    [Page 42]

RFC 2233            Interfaces Group MIB using SMIv2       November 1997


              ifCounterDiscontinuityTime."
      ::= { ifXEntry 9 }

  ifHCOutOctets OBJECT-TYPE
      SYNTAX      Counter64
      MAX-ACCESS  read-only
      STATUS      current
      DESCRIPTION
              "The total number of octets transmitted out of the
              interface, including framing characters.  This object
              is a 64-bit version of ifOutOctets.

              Discontinuities in the value of this counter can occur
              at re-initialization of the management system, and at
              other times as indicated by the value of
              ifCounterDiscontinuityTime."
      ::= { ifXEntry 10 }

  ifHCOutUcastPkts OBJECT-TYPE
      SYNTAX      Counter64
      MAX-ACCESS  read-only
      STATUS      current
      DESCRIPTION
              "The total number of packets that higher-level
              protocols requested be transmitted, and which were not
              addressed to a multicast or broadcast address at this
              sub-layer, including those that were discarded or not
              sent.  This object is a 64-bit version of
              ifOutUcastPkts.

              Discontinuities in the value of this counter can occur
              at re-initialization of the management system, and at
              other times as indicated by the value of
              ifCounterDiscontinuityTime."
      ::= { ifXEntry 11 }

  ifHCOutMulticastPkts OBJECT-TYPE
      SYNTAX      Counter64
      MAX-ACCESS  read-only
      STATUS      current
      DESCRIPTION
              "The total number of packets that higher-level
              protocols requested be transmitted, and which were
              addressed to a multicast address at this sub-layer,
              including those that were discarded or not sent.  For
              a MAC layer protocol, this includes both Group and
              Functional addresses.  This object is a 64-bit version
              of ifOutMulticastPkts.



McCloghrie & Kastenholz     Standards Track                    [Page 43]

RFC 2233            Interfaces Group MIB using SMIv2       November 1997


              Discontinuities in the value of this counter can occur
              at re-initialization of the management system, and at
              other times as indicated by the value of
              ifCounterDiscontinuityTime."
      ::= { ifXEntry 12 }

  ifHCOutBroadcastPkts OBJECT-TYPE
      SYNTAX      Counter64
      MAX-ACCESS  read-only
      STATUS      current
      DESCRIPTION
              "The total number of packets that higher-level
              protocols requested be transmitted, and which were
              addressed to a broadcast address at this sub-layer,
              including those that were discarded or not sent.  This
              object is a 64-bit version of ifOutBroadcastPkts.

              Discontinuities in the value of this counter can occur
              at re-initialization of the management system, and at
              other times as indicated by the value of
              ifCounterDiscontinuityTime."
      ::= { ifXEntry 13 }

  ifLinkUpDownTrapEnable  OBJECT-TYPE
      SYNTAX      INTEGER { enabled(1), disabled(2) }
      MAX-ACCESS  read-write
      STATUS      current
      DESCRIPTION

              "Indicates whether linkUp/linkDown traps should be
              generated for this interface.

              By default, this object should have the value
              enabled(1) for interfaces which do not operate on
              'top' of any other interface (as defined in the
              ifStackTable), and disabled(2) otherwise."
      ::= { ifXEntry 14 }

  ifHighSpeed OBJECT-TYPE
      SYNTAX      Gauge32
      MAX-ACCESS  read-only
      STATUS      current
      DESCRIPTION
              "An estimate of the interface's current bandwidth in
              units of 1,000,000 bits per second.  If this object
              reports a value of `n' then the speed of the interface
              is somewhere in the range of `n-500,000' to
              `n+499,999'.  For interfaces which do not vary in



McCloghrie & Kastenholz     Standards Track                    [Page 44]

RFC 2233            Interfaces Group MIB using SMIv2       November 1997


              bandwidth or for those where no accurate estimation
              can be made, this object should contain the nominal
              bandwidth.  For a sub-layer which has no concept of
              bandwidth, this object should be zero."
      ::= { ifXEntry 15 }

  ifPromiscuousMode  OBJECT-TYPE
      SYNTAX      TruthValue
      MAX-ACCESS  read-write
      STATUS      current
      DESCRIPTION
              "This object has a value of false(2) if this interface
              only accepts packets/frames that are addressed to this
              station.  This object has a value of true(1) when the
              station accepts all packets/frames transmitted on the
              media.  The value true(1) is only legal on certain
              types of media.  If legal, setting this object to a
              value of true(1) may require the interface to be reset
              before becoming effective.

              The value of ifPromiscuousMode does not affect the
              reception of broadcast and multicast packets/frames by
              the interface."
      ::= { ifXEntry 16 }

  ifConnectorPresent   OBJECT-TYPE
      SYNTAX      TruthValue
      MAX-ACCESS  read-only
      STATUS      current
      DESCRIPTION
              "This object has the value 'true(1)' if the interface
              sublayer has a physical connector and the value
              'false(2)' otherwise."
      ::= { ifXEntry 17 }

  ifAlias   OBJECT-TYPE
      SYNTAX      DisplayString (SIZE(0..64))
      MAX-ACCESS  read-write
      STATUS      current
      DESCRIPTION
              "This object is an 'alias' name for the interface as
              specified by a network manager, and provides a non-
              volatile 'handle' for the interface.

              On the first instantiation of an interface, the value
              of ifAlias associated with that interface is the
              zero-length string.  As and when a value is written
              into an instance of ifAlias through a network



McCloghrie & Kastenholz     Standards Track                    [Page 45]

RFC 2233            Interfaces Group MIB using SMIv2       November 1997


              management set operation, then the agent must retain
              the supplied value in the ifAlias instance associated
              with the same interface for as long as that interface
              remains instantiated, including across all re-
              initializations/reboots of the network management
              system, including those which result in a change of
              the interface's ifIndex value.

              An example of the value which a network manager might
              store in this object for a WAN interface is the
              (Telco's) circuit number/identifier of the interface.

              Some agents may support write-access only for
              interfaces having particular values of ifType.  An
              agent which supports write access to this object is
              required to keep the value in non-volatile storage,
              but it may limit the length of new values depending on
              how much storage is already occupied by the current
              values for other interfaces."
      ::= { ifXEntry 18 }

  ifCounterDiscontinuityTime OBJECT-TYPE
      SYNTAX      TimeStamp
      MAX-ACCESS  read-only
      STATUS      current
      DESCRIPTION
              "The value of sysUpTime on the most recent occasion at
              which any one or more of this interface's counters
              suffered a discontinuity.  The relevant counters are
              the specific instances associated with this interface
              of any Counter32 or Counter64 object contained in the
              ifTable or ifXTable.  If no such discontinuities have
              occurred since the last re-initialization of the local
              management subsystem, then this object contains a zero
              value."
      ::= { ifXEntry 19 }


  --           The Interface Stack Group
  --
  -- Implementation of this group is mandatory for all systems
  --

  ifStackTable  OBJECT-TYPE
       SYNTAX        SEQUENCE OF IfStackEntry
       MAX-ACCESS    not-accessible
       STATUS        current
       DESCRIPTION



McCloghrie & Kastenholz     Standards Track                    [Page 46]

RFC 2233            Interfaces Group MIB using SMIv2       November 1997


              "The table containing information on the relationships
              between the multiple sub-layers of network interfaces.
              In particular, it contains information on which sub-
              layers run 'on top of' which other sub-layers, where
              each sub-layer corresponds to a conceptual row in the
              ifTable.  For example, when the sub-layer with ifIndex
              value x runs over the sub-layer with ifIndex value y,
              then this table contains:

                ifStackStatus.x.y=active

              For each ifIndex value, I, which identifies an active
              interface, there are always at least two instantiated
              rows in this table associated with I.  For one of
              these rows, I is the value of ifStackHigherLayer; for
              the other, I is the value of ifStackLowerLayer.  (If I
              is not involved in multiplexing, then these are the
              only two rows associated with I.)

              For example, two rows exist even for an interface
              which has no others stacked on top or below it:

                ifStackStatus.0.x=active
                ifStackStatus.x.0=active "
       ::= { ifMIBObjects 2 }


  ifStackEntry  OBJECT-TYPE
       SYNTAX        IfStackEntry
       MAX-ACCESS    not-accessible
       STATUS        current
       DESCRIPTION
              "Information on a particular relationship between two
              sub-layers, specifying that one sub-layer runs on
              'top' of the other sub-layer.  Each sub-layer
              corresponds to a conceptual row in the ifTable."
       INDEX { ifStackHigherLayer, ifStackLowerLayer }
       ::= { ifStackTable 1 }


  IfStackEntry ::=
      SEQUENCE {
          ifStackHigherLayer  Integer32,
          ifStackLowerLayer   Integer32,
          ifStackStatus       RowStatus
       }





McCloghrie & Kastenholz     Standards Track                    [Page 47]

RFC 2233            Interfaces Group MIB using SMIv2       November 1997


  ifStackHigherLayer  OBJECT-TYPE
       SYNTAX        Integer32
       MAX-ACCESS    not-accessible
       STATUS        current
       DESCRIPTION
              "The value of ifIndex corresponding to the higher
              sub-layer of the relationship, i.e., the sub-layer
              which runs on 'top' of the sub-layer identified by the
              corresponding instance of ifStackLowerLayer.  If there
              is no higher sub-layer (below the internetwork layer),
              then this object has the value 0."
       ::= { ifStackEntry 1 }


  ifStackLowerLayer  OBJECT-TYPE
       SYNTAX        Integer32
       MAX-ACCESS    not-accessible
       STATUS        current
       DESCRIPTION
              "The value of ifIndex corresponding to the lower sub-
              layer of the relationship, i.e., the sub-layer which
              runs 'below' the sub-layer identified by the
              corresponding instance of ifStackHigherLayer.  If
              there is no lower sub-layer, then this object has the
              value 0."
       ::= { ifStackEntry 2 }


  ifStackStatus  OBJECT-TYPE
      SYNTAX         RowStatus
      MAX-ACCESS     read-create
      STATUS         current
      DESCRIPTION
              "The status of the relationship between two sub-
              layers.

              Changing the value of this object from 'active' to
              'notInService' or 'destroy' will likely have
              consequences up and down the interface stack.  Thus,
              write access to this object is likely to be
              inappropriate for some types of interfaces, and many
              implementations will choose not to support write-
              access for any type of interface."
      ::= { ifStackEntry 3 }

  ifStackLastChange OBJECT-TYPE
      SYNTAX         TimeTicks
      MAX-ACCESS     read-only



McCloghrie & Kastenholz     Standards Track                    [Page 48]

RFC 2233            Interfaces Group MIB using SMIv2       November 1997


      STATUS         current
      DESCRIPTION
              "The value of sysUpTime at the time of the last change
              of the (whole) interface stack.  A change of the
              interface stack is defined to be any creation,
              deletion, or change in value of any instance of
              ifStackStatus.  If the interface stack has been
              unchanged since the last re-initialization of the
              local network management subsystem, then this object
              contains a zero value."
      ::= { ifMIBObjects 6 }


  --   Generic Receive Address Table
  --
  -- This group of objects is mandatory for all types of
  -- interfaces which can receive packets/frames addressed to
  -- more than one address.
  --
  -- This table replaces the ifExtnsRcvAddr table.  The main
  -- difference is that this table makes use of the RowStatus
  -- textual convention, while ifExtnsRcvAddr did not.

  ifRcvAddressTable  OBJECT-TYPE
      SYNTAX      SEQUENCE OF IfRcvAddressEntry
      MAX-ACCESS  not-accessible
      STATUS      current
      DESCRIPTION
              "This table contains an entry for each address
              (broadcast, multicast, or uni-cast) for which the
              system will receive packets/frames on a particular
              interface, except as follows:

              - for an interface operating in promiscuous mode,
              entries are only required for those addresses for
              which the system would receive frames were it not
              operating in promiscuous mode.

              - for 802.5 functional addresses, only one entry is
              required, for the address which has the functional
              address bit ANDed with the bit mask of all functional
              addresses for which the interface will accept frames.

              A system is normally able to use any unicast address
              which corresponds to an entry in this table as a
              source address."
      ::= { ifMIBObjects 4 }




McCloghrie & Kastenholz     Standards Track                    [Page 49]

RFC 2233            Interfaces Group MIB using SMIv2       November 1997


  ifRcvAddressEntry  OBJECT-TYPE
      SYNTAX      IfRcvAddressEntry
      MAX-ACCESS  not-accessible
      STATUS      current
      DESCRIPTION
              "A list of objects identifying an address for which
              the system will accept packets/frames on the
              particular interface identified by the index value
              ifIndex."
      INDEX  { ifIndex, ifRcvAddressAddress }
      ::= { ifRcvAddressTable 1 }

  IfRcvAddressEntry ::=
      SEQUENCE {
          ifRcvAddressAddress   PhysAddress,
          ifRcvAddressStatus    RowStatus,
          ifRcvAddressType      INTEGER
      }

  ifRcvAddressAddress OBJECT-TYPE
      SYNTAX      PhysAddress
      MAX-ACCESS  not-accessible
      STATUS      current
      DESCRIPTION
              "An address for which the system will accept
              packets/frames on this entry's interface."

      ::= { ifRcvAddressEntry 1 }

  ifRcvAddressStatus OBJECT-TYPE
      SYNTAX      RowStatus
      MAX-ACCESS  read-create
      STATUS      current
      DESCRIPTION
              "This object is used to create and delete rows in the
              ifRcvAddressTable."

      ::= { ifRcvAddressEntry 2 }

  ifRcvAddressType OBJECT-TYPE
      SYNTAX      INTEGER {
                      other(1),
                      volatile(2),
                      nonVolatile(3)
                  }

      MAX-ACCESS  read-create
      STATUS      current



McCloghrie & Kastenholz     Standards Track                    [Page 50]

RFC 2233            Interfaces Group MIB using SMIv2       November 1997


      DESCRIPTION
              "This object has the value nonVolatile(3) for those
              entries in the table which are valid and will not be
              deleted by the next restart of the managed system.
              Entries having the value volatile(2) are valid and
              exist, but have not been saved, so that will not exist
              after the next restart of the managed system.  Entries
              having the value other(1) are valid and exist but are
              not classified as to whether they will continue to
              exist after the next restart."

      DEFVAL  { volatile }
      ::= { ifRcvAddressEntry 3 }

  -- definition of interface-related traps.

  linkDown NOTIFICATION-TYPE
          OBJECTS { ifIndex, ifAdminStatus, ifOperStatus }
          STATUS  current
          DESCRIPTION
              "A linkDown trap signifies that the SNMPv2 entity,
              acting in an agent role, has detected that the
              ifOperStatus object for one of its communication links
              is about to enter the down state from some other state
              (but not from the notPresent state).  This other state
              is indicated by the included value of ifOperStatus."
      ::= { snmpTraps 3 }

  linkUp NOTIFICATION-TYPE
          OBJECTS { ifIndex, ifAdminStatus, ifOperStatus }
          STATUS  current
          DESCRIPTION
              "A linkDown trap signifies that the SNMPv2 entity,
              acting in an agent role, has detected that the
              ifOperStatus object for one of its communication links
              left the down state and transitioned into some other
              state (but not into the notPresent state).  This other
              state is indicated by the included value of
              ifOperStatus."
      ::= { snmpTraps 4 }

  -- conformance information

  ifConformance OBJECT IDENTIFIER ::= { ifMIB 2 }

  ifGroups      OBJECT IDENTIFIER ::= { ifConformance 1 }
  ifCompliances OBJECT IDENTIFIER ::= { ifConformance 2 }




McCloghrie & Kastenholz     Standards Track                    [Page 51]

RFC 2233            Interfaces Group MIB using SMIv2       November 1997


  -- compliance statements

  ifCompliance2 MODULE-COMPLIANCE
      STATUS  current
      DESCRIPTION
              "The compliance statement for SNMPv2 entities which
              have network interfaces."

      MODULE  -- this module
          MANDATORY-GROUPS { ifGeneralInformationGroup, ifStackGroup2,
                             ifCounterDiscontinuityGroup }

          GROUP       ifFixedLengthGroup
          DESCRIPTION
              "This group is mandatory for all network interfaces
              which are character-oriented or transmit data in
              fixed-length transmission units."

          GROUP       ifHCFixedLengthGroup
          DESCRIPTION
              "This group is mandatory only for those network
              interfaces which are character-oriented or transmit
              data in fixed-length transmission units, and for which
              the value of the corresponding instance of ifSpeed is
              greater than 20,000,000 bits/second."

          GROUP       ifPacketGroup
          DESCRIPTION
              "This group is mandatory for all network interfaces
              which are packet-oriented."

          GROUP       ifHCPacketGroup
          DESCRIPTION
              "This group is mandatory only for those network
              interfaces which are packet-oriented and for which the
              value of the corresponding instance of ifSpeed is
              greater than 650,000,000 bits/second."

          GROUP       ifRcvAddressGroup
          DESCRIPTION
              "The applicability of this group MUST be defined by
              the media-specific MIBs.  Media-specific MIBs must
              define the exact meaning, use, and semantics of the
              addresses in this group."







McCloghrie & Kastenholz     Standards Track                    [Page 52]

RFC 2233            Interfaces Group MIB using SMIv2       November 1997


          OBJECT      ifLinkUpDownTrapEnable
          MIN-ACCESS  read-only
          DESCRIPTION
              "Write access is not required."

          OBJECT      ifPromiscuousMode
          MIN-ACCESS  read-only
          DESCRIPTION
              "Write access is not required."

          OBJECT      ifStackStatus
          SYNTAX      INTEGER { active(1) } -- subset of RowStatus
          MIN-ACCESS  read-only
          DESCRIPTION
              "Write access is not required, and only one of the six
              enumerated values for the RowStatus textual convention
              need be supported, specifically: active(1)."

          OBJECT       ifAdminStatus
          SYNTAX       INTEGER { up(1), down(2) }
          MIN-ACCESS   read-only
          DESCRIPTION
              "Write access is not required, nor is support for the
              value testing(3)."

          OBJECT       ifAlias
          MIN-ACCESS   read-only
          DESCRIPTION
              "Write access is not required."

      ::= { ifCompliances 2 }

  -- units of conformance

  ifGeneralInformationGroup    OBJECT-GROUP
      OBJECTS { ifIndex, ifDescr, ifType, ifSpeed, ifPhysAddress,
                ifAdminStatus, ifOperStatus, ifLastChange,
                ifLinkUpDownTrapEnable, ifConnectorPresent,
                ifHighSpeed, ifName, ifNumber, ifAlias,
                ifTableLastChange }
      STATUS  current
      DESCRIPTION
              "A collection of objects providing information
              applicable to all network interfaces."
      ::= { ifGroups 10 }

  -- the following five groups are mutually exclusive; at most
  -- one of these groups is implemented for any interface



McCloghrie & Kastenholz     Standards Track                    [Page 53]

RFC 2233            Interfaces Group MIB using SMIv2       November 1997


  ifFixedLengthGroup    OBJECT-GROUP
      OBJECTS { ifInOctets, ifOutOctets, ifInUnknownProtos,
                ifInErrors, ifOutErrors }
      STATUS  current
      DESCRIPTION
              "A collection of objects providing information
              specific to non-high speed (non-high speed interfaces
              transmit and receive at speeds less than or equal to
              20,000,000 bits/second) character-oriented or fixed-
              length-transmission network interfaces."
      ::= { ifGroups 2 }

  ifHCFixedLengthGroup    OBJECT-GROUP
      OBJECTS { ifHCInOctets, ifHCOutOctets,
                ifInOctets, ifOutOctets, ifInUnknownProtos,
                ifInErrors, ifOutErrors }
      STATUS  current
      DESCRIPTION
              "A collection of objects providing information
              specific to high speed (greater than 20,000,000
              bits/second) character-oriented or fixed-length-
              transmission network interfaces."
      ::= { ifGroups 3 }

  ifPacketGroup    OBJECT-GROUP
      OBJECTS { ifInOctets, ifOutOctets, ifInUnknownProtos,
                ifInErrors, ifOutErrors,
                ifMtu, ifInUcastPkts, ifInMulticastPkts,
                ifInBroadcastPkts, ifInDiscards,
                ifOutUcastPkts, ifOutMulticastPkts,
                ifOutBroadcastPkts, ifOutDiscards,
                ifPromiscuousMode }
      STATUS  current
      DESCRIPTION
              "A collection of objects providing information
              specific to non-high speed (non-high speed interfaces
              transmit and receive at speeds less than or equal to
              20,000,000 bits/second) packet-oriented network
              interfaces."
      ::= { ifGroups 4 }

  ifHCPacketGroup    OBJECT-GROUP
      OBJECTS { ifHCInOctets, ifHCOutOctets,
                ifInOctets, ifOutOctets, ifInUnknownProtos,
                ifInErrors, ifOutErrors,
                ifMtu, ifInUcastPkts, ifInMulticastPkts,
                ifInBroadcastPkts, ifInDiscards,
                ifOutUcastPkts, ifOutMulticastPkts,



McCloghrie & Kastenholz     Standards Track                    [Page 54]

RFC 2233            Interfaces Group MIB using SMIv2       November 1997


                ifOutBroadcastPkts, ifOutDiscards,
                ifPromiscuousMode }
      STATUS  current
      DESCRIPTION
              "A collection of objects providing information
              specific to high speed (greater than 20,000,000
              bits/second but less than or equal to 650,000,000
              bits/second) packet-oriented network interfaces."
      ::= { ifGroups 5 }

  ifVHCPacketGroup    OBJECT-GROUP
      OBJECTS { ifHCInUcastPkts, ifHCInMulticastPkts,
                ifHCInBroadcastPkts, ifHCOutUcastPkts,
                ifHCOutMulticastPkts, ifHCOutBroadcastPkts,
                ifHCInOctets, ifHCOutOctets,
                ifInOctets, ifOutOctets, ifInUnknownProtos,
                ifInErrors, ifOutErrors,
                ifMtu, ifInUcastPkts, ifInMulticastPkts,
                ifInBroadcastPkts, ifInDiscards,
                ifOutUcastPkts, ifOutMulticastPkts,
                ifOutBroadcastPkts, ifOutDiscards,
                ifPromiscuousMode }
      STATUS  current
      DESCRIPTION
              "A collection of objects providing information
              specific to higher speed (greater than 650,000,000
              bits/second) packet-oriented network interfaces."
      ::= { ifGroups 6 }

  ifRcvAddressGroup    OBJECT-GROUP
      OBJECTS { ifRcvAddressStatus, ifRcvAddressType }
      STATUS  current
      DESCRIPTION
              "A collection of objects providing information on the
              multiple addresses which an interface receives."
      ::= { ifGroups 7 }

  ifStackGroup2    OBJECT-GROUP
      OBJECTS { ifStackStatus, ifStackLastChange }
      STATUS  current
      DESCRIPTION
              "A collection of objects providing information on the
              layering of MIB-II interfaces."
      ::= { ifGroups 11 }

  ifCounterDiscontinuityGroup  OBJECT-GROUP
      OBJECTS { ifCounterDiscontinuityTime }
      STATUS  current



McCloghrie & Kastenholz     Standards Track                    [Page 55]

RFC 2233            Interfaces Group MIB using SMIv2       November 1997


      DESCRIPTION
              "A collection of objects providing information
              specific to interface counter discontinuities."
      ::= { ifGroups 13 }

  -- Deprecated Definitions - Objects


  --
  --    The Interface Test Table
  --
  -- This group of objects is optional.  However, a media-specific
  -- MIB may make implementation of this group mandatory.
  --
  -- This table replaces the ifExtnsTestTable
  --

  ifTestTable   OBJECT-TYPE
      SYNTAX      SEQUENCE OF IfTestEntry
      MAX-ACCESS  not-accessible
      STATUS      deprecated
      DESCRIPTION
              "This table contains one entry per interface.  It
              defines objects which allow a network manager to
              instruct an agent to test an interface for various
              faults.  Tests for an interface are defined in the
              media-specific MIB for that interface.  After invoking
              a test, the object ifTestResult can be read to
              determine the outcome.  If an agent can not perform
              the test, ifTestResult is set to so indicate.  The
              object ifTestCode can be used to provide further
              test-specific or interface-specific (or even
              enterprise-specific) information concerning the
              outcome of the test.  Only one test can be in progress
              on each interface at any one time.  If one test is in
              progress when another test is invoked, the second test
              is rejected.  Some agents may reject a test when a
              prior test is active on another interface.

              Before starting a test, a manager-station must first
              obtain 'ownership' of the entry in the ifTestTable for
              the interface to be tested.  This is accomplished with
              the ifTestId and ifTestStatus objects as follows:

           try_again:
               get (ifTestId, ifTestStatus)
               while (ifTestStatus != notInUse)
                   /*



McCloghrie & Kastenholz     Standards Track                    [Page 56]

RFC 2233            Interfaces Group MIB using SMIv2       November 1997


                    * Loop while a test is running or some other
                    * manager is configuring a test.
                    */
                   short delay
                   get (ifTestId, ifTestStatus)
               }

               /*
                * Is not being used right now -- let's compete
                * to see who gets it.
                */
               lock_value = ifTestId

               if ( set(ifTestId = lock_value, ifTestStatus = inUse,
                        ifTestOwner = 'my-IP-address') == FAILURE)
                   /*
                    * Another manager got the ifTestEntry -- go
                    * try again
                    */
                   goto try_again;

               /*
                * I have the lock
                */
               set up any test parameters.

               /*
                * This starts the test
                */
               set(ifTestType = test_to_run);

               wait for test completion by polling ifTestResult

               when test completes, agent sets ifTestResult
                    agent also sets ifTestStatus = 'notInUse'

               retrieve any additional test results, and ifTestId

               if (ifTestId == lock_value+1) results are valid

             A manager station first retrieves the value of the
             appropriate ifTestId and ifTestStatus objects,
             periodically repeating the retrieval if necessary,
             until the value of ifTestStatus is 'notInUse'.  The
             manager station then tries to set the same ifTestId
             object to the value it just retrieved, the same
             ifTestStatus object to 'inUse', and the corresponding
             ifTestOwner object to a value indicating itself.  If



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             the set operation succeeds then the manager has
             obtained ownership of the ifTestEntry, and the value of
             the ifTestId object is incremented by the agent (per
             the semantics of TestAndIncr).  Failure of the set
             operation indicates that some other manager has
             obtained ownership of the ifTestEntry.

             Once ownership is obtained, any test parameters can be
             setup, and then the test is initiated by setting
             ifTestType.  On completion of the test, the agent sets
             ifTestStatus to 'notInUse'.  Once this occurs, the
             manager can retrieve the results.  In the (rare) event
             that the invocation of tests by two network managers
             were to overlap, then there would be a possibility that
             the first test's results might be overwritten by the
             second test's results prior to the first results being
             read.  This unlikely circumstance can be detected by a
             network manager retrieving ifTestId at the same time as
             retrieving the test results, and ensuring that the
             results are for the desired request.

             If ifTestType is not set within an abnormally long
             period of time after ownership is obtained, the agent
             should time-out the manager, and reset the value of the
             ifTestStatus object back to 'notInUse'.  It is
             suggested that this time-out period be 5 minutes.

             In general, a management station must not retransmit a
             request to invoke a test for which it does not receive
             a response; instead, it properly inspects an agent's
             MIB to determine if the invocation was successful.
             Only if the invocation was unsuccessful, is the
             invocation request retransmitted.

             Some tests may require the interface to be taken off-
             line in order to execute them, or may even require the
             agent to reboot after completion of the test.  In these
             circumstances, communication with the management
             station invoking the test may be lost until after
             completion of the test.  An agent is not required to
             support such tests.  However, if such tests are
             supported, then the agent should make every effort to
             transmit a response to the request which invoked the
             test prior to losing communication.  When the agent is
             restored to normal service, the results of the test are
             properly made available in the appropriate objects.
             Note that this requires that the ifIndex value assigned
             to an interface must be unchanged even if the test



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             causes a reboot.  An agent must reject any test for
             which it cannot, perhaps due to resource constraints,
             make available at least the minimum amount of
             information after that test completes."
      ::= { ifMIBObjects 3 }

  ifTestEntry OBJECT-TYPE
      SYNTAX       IfTestEntry
      MAX-ACCESS   not-accessible
      STATUS       deprecated
      DESCRIPTION
              "An entry containing objects for invoking tests on an
              interface."
      AUGMENTS  { ifEntry }
      ::= { ifTestTable 1 }

  IfTestEntry ::=
      SEQUENCE {
          ifTestId           TestAndIncr,
          ifTestStatus       INTEGER,
          ifTestType         AutonomousType,
          ifTestResult       INTEGER,
          ifTestCode         OBJECT IDENTIFIER,
          ifTestOwner        OwnerString
      }

  ifTestId         OBJECT-TYPE
      SYNTAX       TestAndIncr
      MAX-ACCESS   read-write
      STATUS       deprecated
      DESCRIPTION
              "This object identifies the current invocation of the
              interface's test."
      ::= { ifTestEntry 1 }

  ifTestStatus     OBJECT-TYPE
      SYNTAX       INTEGER { notInUse(1), inUse(2) }
      MAX-ACCESS   read-write
      STATUS       deprecated
      DESCRIPTION
              "This object indicates whether or not some manager
              currently has the necessary 'ownership' required to
              invoke a test on this interface.  A write to this
              object is only successful when it changes its value
              from 'notInUse(1)' to 'inUse(2)'.  After completion of
              a test, the agent resets the value back to
              'notInUse(1)'."
      ::= { ifTestEntry 2 }



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  ifTestType       OBJECT-TYPE
      SYNTAX       AutonomousType
      MAX-ACCESS   read-write
      STATUS       deprecated
      DESCRIPTION
              "A control variable used to start and stop operator-
              initiated interface tests.  Most OBJECT IDENTIFIER
              values assigned to tests are defined elsewhere, in
              association with specific types of interface.
              However, this document assigns a value for a full-
              duplex loopback test, and defines the special meanings
              of the subject identifier:

                  noTest  OBJECT IDENTIFIER ::= { 0 0 }

              When the value noTest is written to this object, no
              action is taken unless a test is in progress, in which
              case the test is aborted.  Writing any other value to
              this object is only valid when no test is currently in
              progress, in which case the indicated test is
              initiated.

              When read, this object always returns the most recent
              value that ifTestType was set to.  If it has not been
              set since the last initialization of the network
              management subsystem on the agent, a value of noTest
              is returned."
      ::= { ifTestEntry 3 }

  ifTestResult  OBJECT-TYPE
      SYNTAX       INTEGER {
                       none(1),          -- no test yet requested
                       success(2),
                       inProgress(3),
                       notSupported(4),
                       unAbleToRun(5),   -- due to state of system
                       aborted(6),
                       failed(7)
                   }
      MAX-ACCESS   read-only
      STATUS       deprecated
      DESCRIPTION
              "This object contains the result of the most recently
              requested test, or the value none(1) if no tests have
              been requested since the last reset.  Note that this
              facility provides no provision for saving the results
              of one test when starting another, as could be
              required if used by multiple managers concurrently."



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      ::= { ifTestEntry 4 }

  ifTestCode  OBJECT-TYPE
      SYNTAX       OBJECT IDENTIFIER
      MAX-ACCESS   read-only
      STATUS       deprecated
      DESCRIPTION
              "This object contains a code which contains more
              specific information on the test result, for example
              an error-code after a failed test.  Error codes and
              other values this object may take are specific to the
              type of interface and/or test.  The value may have the
              semantics of either the AutonomousType or
              InstancePointer textual conventions as defined in RFC
              1903.  The identifier:

                  testCodeUnknown  OBJECT IDENTIFIER ::= { 0 0 }

              is defined for use if no additional result code is
              available."
      ::= { ifTestEntry 5 }

  ifTestOwner      OBJECT-TYPE
      SYNTAX       OwnerString
      MAX-ACCESS   read-write
      STATUS       deprecated
      DESCRIPTION
              "The entity which currently has the 'ownership'
              required to invoke a test on this interface."
      ::= { ifTestEntry 6 }

  -- Deprecated Definitions - Groups


  ifGeneralGroup    OBJECT-GROUP
      OBJECTS { ifDescr, ifType, ifSpeed, ifPhysAddress,
                ifAdminStatus, ifOperStatus, ifLastChange,
                ifLinkUpDownTrapEnable, ifConnectorPresent,
                ifHighSpeed, ifName }
      STATUS  deprecated
      DESCRIPTION
              "A collection of objects deprecated in favour of
              ifGeneralInformationGroup."
      ::= { ifGroups 1 }


  ifTestGroup    OBJECT-GROUP
      OBJECTS { ifTestId, ifTestStatus, ifTestType,



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                ifTestResult, ifTestCode, ifTestOwner }
      STATUS  deprecated
      DESCRIPTION
              "A collection of objects providing the ability to
              invoke tests on an interface."
      ::= { ifGroups 8 }


  ifStackGroup    OBJECT-GROUP
      OBJECTS { ifStackStatus }
      STATUS  deprecated
      DESCRIPTION
              "The previous collection of objects providing
              information on the layering of MIB-II interfaces."
      ::= { ifGroups 9 }


  ifOldObjectsGroup    OBJECT-GROUP
      OBJECTS { ifInNUcastPkts, ifOutNUcastPkts,
                ifOutQLen, ifSpecific }
      STATUS  deprecated
      DESCRIPTION
              "The collection of objects deprecated from the
              original MIB-II interfaces group."
      ::= { ifGroups 12 }


  -- Deprecated Definitions - Compliance

  ifCompliance MODULE-COMPLIANCE
      STATUS  deprecated
      DESCRIPTION
              "The previous compliance statement for SNMPv2 entities
              which have network interfaces."

      MODULE  -- this module
          MANDATORY-GROUPS { ifGeneralGroup, ifStackGroup }

          GROUP       ifFixedLengthGroup
          DESCRIPTION
              "This group is mandatory for all network interfaces
              which are character-oriented or transmit data in
              fixed-length transmission units."

          GROUP       ifHCFixedLengthGroup
          DESCRIPTION
              "This group is mandatory only for those network
              interfaces which are character-oriented or transmit



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              data in fixed-length transmission units, and for which
              the value of the corresponding instance of ifSpeed is
              greater than 20,000,000 bits/second."

          GROUP       ifPacketGroup
          DESCRIPTION
              "This group is mandatory for all network interfaces
              which are packet-oriented."

          GROUP       ifHCPacketGroup
          DESCRIPTION
              "This group is mandatory only for those network
              interfaces which are packet-oriented and for which the
              value of the corresponding instance of ifSpeed is
              greater than 650,000,000 bits/second."

          GROUP       ifTestGroup
          DESCRIPTION
              "This group is optional.  Media-specific MIBs which
              require interface tests are strongly encouraged to use
              this group for invoking tests and reporting results.
              A medium specific MIB which has mandatory tests may
              make implementation of this group mandatory."

          GROUP       ifRcvAddressGroup
          DESCRIPTION
              "The applicability of this group MUST be defined by
              the media-specific MIBs.  Media-specific MIBs must
              define the exact meaning, use, and semantics of the
              addresses in this group."

          OBJECT      ifLinkUpDownTrapEnable
          MIN-ACCESS  read-only
          DESCRIPTION
              "Write access is not required."

          OBJECT      ifPromiscuousMode
          MIN-ACCESS  read-only
          DESCRIPTION
              "Write access is not required."

          OBJECT      ifStackStatus
          SYNTAX      INTEGER { active(1) } -- subset of RowStatus
          MIN-ACCESS  read-only
          DESCRIPTION
              "Write access is not required, and only one of the six
              enumerated values for the RowStatus textual convention
              need be supported, specifically: active(1)."



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          OBJECT       ifAdminStatus
          SYNTAX       INTEGER { up(1), down(2) }
          MIN-ACCESS   read-only
          DESCRIPTION
              "Write access is not required, nor is support for the
              value testing(3)."
      ::= { ifCompliances 1 }

  END

7.  Acknowledgements

  This memo has been produced by the IETF's Interfaces MIB working-
  group.

  The original proposal evolved from conversations and discussions with
  many people, including at least the following: Fred Baker, Ted
  Brunner, Chuck Davin, Jeremy Greene, Marshall Rose, Kaj Tesink, and
  Dean Throop.

8.  References

  [1]  Case, J., McCloghrie, K., Rose, M., and
       S. Waldbusser, "Structure of Management Information for
       version 2 of the Simple Network Management Protocol
       (SNMPv2)", RFC 1902, January 1996.

  [2]  Case, J., McCloghrie, K., Rose, M., and
       S. Waldbusser, "Textual Conventions for version 2 of the
       Simple Network Management Protocol (SNMPv2)", RFC 1903,
       January 1996.

  [3]  Case, J., McCloghrie, K., Rose, M., and
       S. Waldbusser, "Protocol Operations for version 2 of the
       Simple Network Management Protocol (SNMPv2)", RFC 1905,
       January 1996.

  [4]  McCloghrie, K., and M. Rose, "Management Information Base for
       Network Management of TCP/IP-based internets - MIB-II", STD
       17, RFC 1213, March 1991.

  [5]  Case, J., Fedor, M., Schoffstall, M., and J. Davin, "Simple
       Network Management Protocol", STD 15, RFC 1157, May 1990.

  [6]  Postel, J., "Internet Protocol", STD 5, RFC 791, September 1981.

  [7]  McCloghrie, K., "Extensions to the Generic-Interface MIB", RFC
       1229, May 1991.



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  [8]  ATM Forum Technical Committee, "LAN Emulation Client
       Management: Version 1.0 Specification", af-lane-0044.000, ATM
       Forum, September 1995.

  [9]  Stewart, B., "Definitions of Managed Objects for Character
       Stream Devices using SMIv2", RFC 1658, July 1994.

  [10] Bradner, S., "Key words for use in RFCs to Indicate
       Requirements Levels", RFC 2119, March 1997.

9.  Security Considerations

  This MIB contains both readable objects whose values provide the
  number and status of a device's network interfaces, and write-able
  objects which allow an administrator to control the interfaces and to
  perform tests on the interfaces.  Unauthorized access to the readable
  objects is relatively innocuous.  Unauthorized access to the write-
  able objects could cause a denial of service, or in combination with
  other (e.g., physical) security breaches, could cause unauthorized
  connectivity to a device.

10.  Authors' Addresses

  Keith McCloghrie
  Cisco Systems, Inc.
  170 West Tasman Drive
  San Jose, CA  95134-1706

  Phone: 408-526-5260
  EMail: [email protected]


  Frank Kastenholz
  FTP Software
  2 High Street
  North Andover, Mass. USA 01845

  Phone: 508-685-4000
  EMail: [email protected]












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11.  Full Copyright Statement

  Copyright (C) The Internet Society (1997).  All Rights Reserved.

  This document and translations of it may be copied and furnished to
  others, and derivative works that comment on or otherwise explain it
  or assist in its implementation may be prepared, copied, published
  and distributed, in whole or in part, without restriction of any
  kind, provided that the above copyright notice and this paragraph are
  included on all such copies and derivative works.  However, this
  document itself may not be modified in any way, such as by removing
  the copyright notice or references to the Internet Society or other
  Internet organizations, except as needed for the purpose of
  developing Internet standards in which case the procedures for
  copyrights defined in the Internet Standards process must be
  followed, or as required to translate it into languages other than
  English.

  The limited permissions granted above are perpetual and will not be
  revoked by the Internet Society or its successors or assigns.

  This document and the information contained herein is provided on an
  "AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING
  TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING
  BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION
  HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF
  MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.
























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