_________________________________________________________________

     This page was last updated January 13th 1997.

          MINI HOW-TO ON SETTING UP IP ALIASING ON A LINUX MACHINE

 _GNU Copyleft 1996/1997 Harish Pillay ([email protected])_

   Primary site: http://home.pacific.net.sg/~harish/linuxipalias.html

  Synopsis:

  This is a cook book recipe on how to set up and run IP aliasing on a
  Linux box. In addition, there are instructions on how to also set up
  the machine to receive e-mail on the aliased IP #s.

  My setup:
    * Latest kernel (2.0.27 - from
      ftp.funet.fi:/pub/Linux/kernel/src/v2.0) - has worked since
      1.3.7x.
    * IP Alias compiled as a loadable module. You would have indicated
      in the "make config" command to make your kernel, that you want
      the IP Masq to be compiled as a (M)odule. Check the Modules HOW-TO
      (if that exists) or check the info in
      /usr/src/linux/Documentation/modules.txt.
    * I have to support 2 additional IPs over and above the IP already
      allocated to me.
    * A D-Link DE620 pocket adapter (not important, works with any Linux
      supported network adapter).

  Commands:
    * First load the IP Alias module (you can skip this step if you
      compiled the module into the kernel):

/sbin/insmod /lib/modules/`uname -r`/ipv4/ip_alias.o
    * Second, setup the loopback, eth0 and all the IP #s beginning with
      the main IP # for the eth0 interface:


/sbin/ifconfig lo 127.0.0.1
/sbin/ifconfig eth0 up
/sbin/ifconfig eth0 172.16.3.1
/sbin/ifconfig eth0:0 172.16.3.10
/sbin/ifconfig eth0:1 172.16.3.100
  172.16.3.1 is the main IP #, while .10 and .100 are the aliases. The
      magic is the eth0:x where x=0,1,2,...n for the different IP #s.
      The main IP # does not need to be aliased.

    * Third, setup the routes. First route the loopback, then the net
      and, finally, the various IP #s starting with the default
      (originally allocated) one:


/sbin/route add -net 127.0.0.0
/sbin/route add -net 172.16.3.0 dev eth0
/sbin/route add -host 172.16.3.1 dev eth0
/sbin/route add -host 172.16.3.10 dev eth0:0
/sbin/route add -host 172.16.3.100 dev eth0:1
/sbin/route add default gw 172.16.3.200

  That's it.

  In the example IP # above, I am using the Private IP #s (RFC 1918) for
  illustrative purposes. Substitute them with your own official or
  private IP #s.

  The example shows only 3 IP #s. The max is defined to be 256 in
  /usr/include/linux/net_alias.h. 256 IP #s on ONE card is a lot :-)!

  Here's what my /sbin/ifconfig looks like:



lo        Link encap:Local Loopback
         inet addr:127.0.0.1  Bcast:127.255.255.255  Mask:255.0.0.0
         UP BROADCAST LOOPBACK RUNNING  MTU:3584  Metric:1
         RX packets:5088 errors:0 dropped:0 overruns:0
         TX packets:5088 errors:0 dropped:0 overruns:0

eth0      Link encap:10Mbps Ethernet  HWaddr 00:8E:B8:83:19:20
         inet addr:172.16.3.1  Bcast:172.16.3.255  Mask:255.255.255.0
         UP BROADCAST RUNNING PROMISC MULTICAST  MTU:1500  Metric:1
         RX packets:334036 errors:0 dropped:0 overruns:0
         TX packets:11605 errors:0 dropped:0 overruns:0
         Interrupt:7 Base address:0x378

eth0:0    Link encap:10Mbps Ethernet  HWaddr 00:8E:B8:83:19:20
         inet addr:172.16.3.10  Bcast:172.16.3.255  Mask:255.255.255.0
         UP BROADCAST RUNNING  MTU:1500  Metric:1
         RX packets:0 errors:0 dropped:0 overruns:0
         TX packets:0 errors:0 dropped:0 overruns:0

eth0:1    Link encap:10Mbps Ethernet  HWaddr 00:8E:B8:83:19:20
         inet addr:172.16.3.100  Bcast:172.16.3.255  Mask:255.255.255.0
         UP BROADCAST RUNNING  MTU:1500  Metric:1
         RX packets:1 errors:0 dropped:0 overruns:0
         TX packets:0 errors:0 dropped:0 overruns:0

  And /proc/net/aliases:

device           family address
eth0:0           2      172.16.3.10
eth0:1           2      172.16.3.100



  And /proc/net/alias_types:

type    name            n_attach
2       ip              2



  Of course, the stuff in /proc/net was created by the ifconfig command
  and not by hand!

  _Question: How can I keep the settings through a reboot?_

  _Answer:_ Whether you are using BSD-style or SysV-style (Redhat for
  example) init, you can always include it in /etc/rc.d/rc.local. Here's
  what I have on my SysV init system (Redhat 3.0.3 and 4.0):

    * My /etc/rc.d/rc.local: (edited to show the relevant portions)


#setting up IP alias interfaces
echo "Setting 172.16.3.1, 172.16.3.10, 172.16.3.100 IP Aliases ..."
/sbin/ifconfig lo 127.0.0.1
/sbin/ifconfig eth0 up
/sbin/ifconfig eth0 172.16.3.1
/sbin/ifconfig eth0:0 172.16.3.10
/sbin/ifconfig eth0:1 172.16.3.100
#setting up the routes
echo "Setting IP routes ..."
/sbin/route add -net 127.0.0.0
/sbin/route add -net 172.16.3.0 dev eth0
/sbin/route add -host 172.16.3.1 eth0
/sbin/route add -host 172.16.3.10 eth0:0
/sbin/route add -host 172.16.3.100 eth0:1
/sbin/route add default gw 172.16.3.200
#

  _Question: How do I set up the IP aliased machine to receive e-mail on
  the various aliased IP #s (on a machine using sendmail)?_

    * _Answer:_ Create (if not already existing) a file called for
      example, /etc/mynames.cw. It does not have to be this exact name
      nor in the /etc directory.

    * In that file, place the official domain names of the aliased IP
      #s. If these aliased IP #s do not have a domain name, then you can
      place the IP # itself.


/etc/mynames.cw:
----------------
# /etc/mynames.cw - include all aliases for your machine here; # is a comment.
domain.one.net
domain.two.com
domain.three.org
4.5.6.7
    * In your sendmail.cf file, where it defines a file class macro Fw,
      add the following:

You are viewing proxied material from ftp.icm.edu.pl. The copyright of proxied material belongs to its original authors. Any comments or complaints in relation to proxied material should be directed to the original authors of the content concerned. Please see the disclaimer for more details.