[TriLUG] Conflicting Default Gateways

[Aaron S. Joyner]

Michael Thompson wrote:

> I don't believe you can have 2 default gateways, even with 2 network
> cards.  The only way to achieve your goal is to use some kind of routing
> protocol that would know if one gateway was down and automatically use
> the other, or policy routing (if destination is <foo> then route through
> gateway <bar>)...
>
> $.02
>
> --mike

The snazzier twist on policy routing is, "if src is <foo> then route 
through <bar>" - that way the app can choose it's source address, and 
there-by which interface it's traffic goes over.  You can also setup 
rules / tables that set your default gateway on a per-connection basis, 
so that if someone sends traffic to your eth1 interface, you don't try 
to respond out eth2 -- a very critical point when dealing with 
consumer-grade lines.  No Cable or DSL provider is going to allow you to 
respond with a source address of an IP that isn't yours - in an attempt 
to prevent spoofing.

Aaron S. Joyner