I just found this message again.

Okay, there has to be a single network in common on both the serial interfaces.

10.1.1.0(eth0)cisco(serial0)192.168.1.1---t1---192.168.1.2(serial0)cisco(eth0)192.168.100.0

route rip2
network 10.1.1.0
network 192.168.100.0
redistribute route