From: Lloyd Zusman <ljz@...>
Date: 2007-01-14T04:56:21+09:00
Subject: Re: Running Webrick alongside IIS on port 80

Robert Klemme <shortcutter@googlemail.com> writes:

> [ ... ]
>
> You actually can have *two* IP addresses on *one* NIC?  Are you sure
> about that?  How would you configure that for example on Linux?

This varies slightly under different flavors of Linux.  On one of the
linux boxes I use (RedHat, kernel version
2.6.9-022stab078.21-enterprise), it's done like this:

  In /etc/sysconfig/network-scripts, the following files exist (IP
  addr's changed):

    ifcfg-venet0
    contents:  DEVICE=venet0
               BOOTPROTO=static
               ONBOOT=yes
               IPADDR=127.0.0.1
               NETMASK=255.255.255.255
               BROADCAST=0.0.0.0

    ifcfg-venet0:0
    contents:  DEVICE=venet0:0
               ONBOOT=yes
               IPADDR=1.2.3.4
               NETMASK=255.255.255.255

    ifcfg-venet0:1
    contents:  DEVICE=venet0:1
               ONBOOT=yes
               IPADDR=1.2.3.5
               NETMASK=255.255.255.255

    ifcfg-venet0:2
    contents:  DEVICE=venet0:2
               ONBOOT=yes
               IPADDR=1.2.3.6
               NETMASK=255.255.255.255

    ifcfg-venet0:3
    contents:  DEVICE=venet0:3
               ONBOOT=yes
               IPADDR=1.2.3.7
               NETMASK=255.255.255.255

  This sets up 127.0.0.1 plus four other IP's.  

  Also, the following fragment exists in the standard, non-modified
  version of /etc/init.d/network that's in use at my site:

    [ ... etc. ... ]

    cd /etc/sysconfig/network-scripts

    . network-functions

    # find all the interfaces besides loopback.
    # ignore aliases, alternative configurations, and editor backup files
    interfaces=`ls ifcfg* | LANG=C egrep -v '(ifcfg-lo|:|rpmsave|rpmorig|rpmnew)' | \
                LANG=C egrep -v '(~|\.bak)$' | \
                LANG=C egrep 'ifcfg-[A-Za-z0-9\._-]+$' | \
                sed 's/^ifcfg-//g'`

    [ ... etc. ... ]

  Later in the script, the $interfaces variable is searched for all
  valid interfaces to start up.

That machine has a single NIC which is configured to listen on multiple
IP's.  The server farm which manages this machine routes the four IP
addresses to this host.  I'm pretty sure that it's not necessary to have
a special NIC for this.


-- 
 Lloyd Zusman
 ljz@asfast.com
 God bless you.