Dual Cisco 2501 router setup

Routers generally have an IP address for each interface, and route layer-3 traffic from interface to interface. Ethernet interfaces aren't the only ones that you have IP addresses on. Some routers have hundreds of real or virtual interfaces, each with their own IP address in different networks.

In general (without doing things like "ip unnumbered" you would assign an additional network to s0 on the first 2501, and another IP in that network to s0 on the 2nd 2501.

Routers don't bridge traffic (unless you setup bridging), they route, so you need to tell routers which interface to route through, and create the routing table to handle all traffic.

So you would setup a static route for 172.16.255.1/16 to route down out the serial interface (either by an IP gateway route, or out the interface itself), and likewise on the other 2501.

Thanks for the quick response. So would the following work fine provided I setup the correct routes after setting up the interfaces correctly?

Switch 1 - Ethernet 1 - 192.168.100.1 Switch 1 - Serial 0 - 192.168.0.1 Switch 2 - Serial 0 - 192.168.0.2 Switch 2 - Ethernet 1 - 172.16.255.1

Sure, that sounds good (although I don't know what context a "switch" would be for a serial interface).