Setting up NT 4 Workstation as a router

I have a multihomed NT4 Workstation with 2 NICS in. I have been trying to set it up as a router/gateway. The subnets are the same ie. 255.255.255.0 and the IP addresses are private and as follows… 192.168.12.6 and 192.168.13.1. I have IP routing enabled and RIP installed but when I traceroute to the 192.168.12.x range it stops after 192.168.13.1. What am I doing wrong?