Two NICs, same network...

["semi linux" <linuxsemi@gmail.com>]

I've got an odd problem where I've got two NICs on the same network
and I want all traffic to one IP to go out one interface and all other
traffic to use the second interface.  I'm going to try an simplify my
actual setup, because a lot of it makes no difference to this post...

I know this has to be a iptables sort of setup since the routing table
can only make a difference on different networks and not based on
looking for a specific IP address.

The question is:

eth0 IP: 10.1.1.1
eth1 IP: 10.1.1.2

target: 10.1.1.3

(these IPs are just examples, there are no hard-fast rules surrounding
the other possibilities)

How do I make sure this goes out eth1 instead of eth0?  Do I use the
mangle rule with the physdev module?

I feel like I'm overlooking something or forgetting my basic network
ideas here...

- Gareth