network brain bender

Stuart Jansen sjansen at
Thu Nov 6 19:22:29 MST 2008

I would like to setup a server with two NICs plugged into two seperate
networks that use the same addresses. The server should be able to
respond to ICMP, DNS, NFS, HTTP & FTP. At first this would seem
ridiculous and impossible, but a little experimenting suggests it
_might_ be possible.

If possible, the result will be a more convenient development/testing
environment with lower RAM requirements.

Using virtual machine, I've setup something like the following:

| |
|             |      |---
|        eth0 |------|
|             |      |---
|             |
|             |      |---
|        eth1 |------|
|             |      |---

Giving eth0 and eth1 the same IPs is preferred. Giving them separate IPs
might still be acceptable.

At first, one network would work and the other would be SOL. Basically,
whoever was first to populate the ARP cache would win. Playing with the
route tables, I've been able to get layer 2 more or less working but now
I'm having problems with layer 3. I'm thinking I may need to rely on the
netfilter conntrack module, but I don't want to go into to much detail
because what I've got isn't quite working and I don't want to stifle
anyone's creativity.

Anyone up for a challenge? I'll give you major geek points.

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