One peculiar router …

* * * * *

One peculiar router …

I decided to poke around a bit with the home router, a Cisco WRVS4400N
Wireless-N Gigabit Security Router [1] and I must say, it's an odd router
from a management point of view.

So I get a list of interfaces (via SNMP (Simple Network Management Protocol))
on the device:

Table: Interface Dump
Status Interface Bytes In Bytes Out
------------------------------
up lo 207454 207454
down ipsec1 0 0
down ipsec2 0 0
down ipsec3 0 0
up br0 304475952 467833506
up ppp0 100525553 80535424
up sit1 0 0
up eth0 246917723 273606969
up eth1 119391487 88802941
up eth2 109882441 191904431
down teql0 0 0
up sit0 0 0
down tunl0 0 0
down gre0 0 0
up ipsec0 0 0

Okay, lo is the local loopback device, I have no idea what br0 is, but I see
eth0, eth1 and eth2 which are obviously the Ethernet ports in use. So, what
do I have plugged in where? Okay, that's easy to determine—unplug a device,
see which interface is marked as “down”. This is typical Cicso behavior,
right?

Okay, I unplug the Mac from the network and I see:

Table: Interface Dump
Status Interface Bytes In Bytes Out
------------------------------
up lo 207454 207454
down ipsec1 0 0
down ipsec2 0 0
down ipsec3 0 0
up br0 304488023 467841666
up ppp0 100526059 80536312
up sit1 0 0
up eth0 246926120 273617295
up eth1 119393091 88804157
up eth2 109888649 191905881
down teql0 0 0
up sit0 0 0
down tunl0 0 0
down gre0 0 0
up ipsec0 0 0

So. It's not going to mark one of the Ethernet ports as being down. Lovely.
Looks like I'm going to have to do this the old fasioned way:

[Physically tracing the wires] [2]

Physically trace each Ethernet cable. Okay, in the above image, the left-most
cable goes out to the Intarwebs. The right-most cable (the blue one, in the
port labeled “4”) goes to the Mac. The one to the left of the blue cable (in
port “3”) goes to my Linux system. The one in port “2” goes to a computer
that is currently turned off. And the one in port “1” (the second on the
left) wraps around and is hanging in front of the shelves (I use that one for
the laptop).

Wait a minute … let me look at the front again …

[Cisco WRVS4400N] [3]

We have the Internet; Mac is at gigabit speed; my Linux system, and … the
turned off system? Really?

Okay, it appears that the Ethernet card in the currently off system receives
just enough power to maintain a connection status; there's probably a “wake-
on-LAN (Local Area Network) [4]” feature on its Ethernet card.

Okay, now that's that's straightened out … um …

eth0, eth1 and eth2 …

Um …

The external ports don't match up with the internal ports. And given that
there's a computer that is turned off, shouldn't one of the Ethernet ports
return no data? And where's eth3?

What exactly is going on?

Okay, put that aside for now. What's the routing table look like?

Table: Routing Table
Dest Mask NextHop Proto Metric Age Interface
------------------------------
0.0.0.0 0.0.0.0 70.XXXXXXXXXX local 0 0 ppp0
127.0.0.0 255.255.0.0 0.0.0.0 local 0 0 sit1
192.168.1.0 255.255.255.0 0.0.0.0 local 0 0 br0
239.0.0.0 255.0.0.0 0.0.0.0 local 0 0 br0
70.XXXXXXXXXX 255.255.255.255 0.0.0.0 local 0 0 ppp0

Um, 70.XXXXXXXXXX isn't my IP (Internet Protocol) address; it's 74.XXXXXXXXX
(I pay extra for a static IP address because of work issues). Okay, it
appears that 70.XXXXXXXXXX is the remote side of my connection, but that
routing (while it works) just looks odd to me. So, what IP addresses are
assigned to which interfaces?

Table: Interfaces
Destination Mask Interface
------------------------------
127.0.0.1 255.0.0.0 lo
192.168.1.1 255.255.255.0 br0
74.XXXXXXXXX 255.255.255.255 ipsec0

Okay, there's my IP address, but it's … ipsec0? Weird. And it seems that br0
is a grouping of all the Ethernet ports.

But really, the mislableled Ethernet ports, the turned off computer sending
and receiving traffic, it just has me skeeved out a bit. And the whole mess
makes it difficult to monitor the network (not that I need to monitor my
network, but Cisco is selling this as a “Small Business” device and a “Small
Business” might want to monitor its network).

Oh, I just thought of something … the wireless interface—it's missing! I
mean, it's missing in the interface list; physically it's there or Bunny
wouldn't be able to use her laptop on the Intarwebs.

This is one strange router …

Update on Tuesday, January 22^nd, 2013

My friend Mark [5] fills me in on what might be happening [6] …

[1] http://www.cisco.com/en/US/products/ps9931/index.html
[2] gopher://gopher.conman.org/IPhlog:2013/01/21/checking-the-router.jpg
[3] gopher://gopher.conman.org/IPhlog:2013/01/21/router-front.jpg
[4] http://en.wikipedia.org/wiki/Wake-on-LAN
[5] http://gladesoft.com/
[6] gopher://gopher.conman.org/0Phlog:2013/01/22.1

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