WINDOWS 2000 AS A ROUTER

I am having a rather strange problem…. i have set up win2k to act as a router between 2 servers on different ip’s & subnets. the router works fine & both sides can ping the router. my problem is that when i use dailup networking i can not access my isp even to download mai. i cannot access the internet either… is there something i am doing wrong ??? My network is between to servers one is on 10.10.0.1 & the other is on 192.168.0.1…..