having 2 interfaces on the same box with the same IP address
repeat after me :
WILL NOT WORK
Well, I can't see why not. Can you explain?
uh, because that's how routing in the server PC works. you have to have a different address for each interface.
your best bet is to either use the same interface (and change one of the client's IP to something else (like 192.168.100.3) like so :
server | __________ client 1 eth0:192.168.100.1 |--------| ethernet |------| 192.168.0.2 | | switch | |__________|------| 192.168.0.3 client 2
or... change one of the subnets to use a different prefix, like so :
Server | | Client 1 eth0:192.168.100.1 |---------| 192.168.100.2 | | Client 2 eth1:192.168.101.1 |------------------------------| 192.168.101.2