[oclug] Subnets with identical addresses... HowTo????

[Sandy Harris]

Greg Franks wrote:
> 
> Is it possible to have two subnets with the same address,  but on
> different interfaces?  eg:
> 
>   eth0: inet addr:10.0.0.1  Bcast:10.0.0.255  Mask:255.255.255.0
>   eth1: inet addr:10.0.0.1  Bcast:10.0.0.255  Mask:255.255.255.0

No. The network is designed to have IP addresses be unique. This is a very
basic assumption; you cannot break it without major work.

You might be able to kluge it somehow with major fiddles at a low
level of the IP stack, but nothing short of that will do it and that
sort of fiddle strikes me as both extremely silly and very expensive.

Why do you want this?
 
> Clearly, these would be on their own disjoint private networks.

On the other hand, it is trivial if you use two different gateway
machines, each masquerading for a 10.0.0.0 private net. Since
the 10.* addresses never appear on the public side of those gates,
no-one outside the private nets sees them.

It is also trivial to have different private nets behind one gate:

   eth0: inet addr:10.0.0.1  Bcast:10.0.0.255  Mask:255.255.255.0
   eth1: inet addr:10.0.1.1  Bcast:10.0.1.255  Mask:255.255.255.0

Why doesn't this do what you want?