RE: IP Aliasing

You won't be able to talk "across the wire" from one port to another aliased port on a single machine. The Linux kernel code itself short-circuits local addresses. My need to do just this could not overcome my lack of insight into where in the kernel to screw around and implement it. (or "deimplement" the optimization). Oh well,

Douglas S. Huneycutt, Sr.
Senior Infosec/IA Engineer
Lockheed Martin Secure Enterprise Systems
9500 Godwin Drive, Manassas VA 20110
703-367-4670 FAX 703-367-3312
doug.huneycutt@lmco.com

-----Original Message-----
From: Chad Morgan [mailto:chad@ns.enhancetheweb.com]
Sent: Thursday, October 11, 2001 12:59 PM
To: debian-firewall@lists.debian.org
Subject: IP Aliasing

I tried asking this in debain-user but didn't get an answer. I thought maybe someone here would be able to help me.

On eth0 I have 216.86.213.93 and on eth0:0 I have 216.86.193.94

I can ping both addresses from that computer but from other computers I can only ping .93 on eth0

When I reverse the situation so that .94 is on eth0 and .93 is on eth0:0 the same is true, I can only access .94 on eth0 from other computers.

What I ultimately want to do is have an aliased IP address fowrard to an internal address for some users that want to use PC Anywhere.

A copy of the output of ifconfig is below.

Chad Morgan

--------------------------

eth0      Link encap:Ethernet HWaddr 00:A0:CC:23:A3:AC
          inet addr:216.86.213.93 Bcast:216.86.213.255 Mask:255.255.255.0
          UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
          RX packets:8862 errors:0 dropped:0 overruns:0 frame:0
          TX packets:16582 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:100
          Interrupt:10 Base address:0x6000

eth0:0    Link encap:Ethernet HWaddr 00:A0:CC:23:A3:AC
          inet addr:216.86.213.94 Bcast:216.86.213.255 Mask:255.255.255.0
          UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
          Interrupt:10 Base address:0x6000

eth1      Link encap:Ethernet HWaddr 00:A0:CC:5A:CB:A2
          inet addr:192.168.0.1 Bcast:192.168.0.255 Mask:255.255.255.0
          UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
          RX packets:13403 errors:0 dropped:0 overruns:0 frame:0
          TX packets:10863 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:100
          Interrupt:11 Base address:0x6100

lo        Link encap:Local Loopback
          inet addr:127.0.0.1 Mask:255.0.0.0
          UP LOOPBACK RUNNING MTU:3924 Metric:1
          RX packets:4272 errors:0 dropped:0 overruns:0 frame:0
          TX packets:4272 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:0