Im stuck trying to think through a routing problem when redesigning our network. What we have is 2 buildings connected through 2 Cisco 2620 routers and a T-1. In addition to that each site has a dedicated T-1 to the internet. Building A is our primary building and has a full class C being routed through the 2620, building B is using NAT to get to the internet through its own T-1 there. This has worked great for many years now, both buildings can get to the internet and communicate with eachother.
But, we've now purchased a 10meg fiber ethernet hand off to the internet to replace the T-1 at building A. In order to interface with this we purchase a cisco 3550 switch and have enabled IP routing. We can route our class C to the internet just fine using the new switch and the new 10 meg line. The real trouble comes in when we try and connect our two buildings, since the connection between the buildings is a serial connection it wont interface with the 3550.
We decided we would try and setup the 2620 router to maintain routing between the buildings. Unfortunately i'm having troulbe figuring out how to do that since our class C no longer resides on the 2620 but on the 3550 which means the 3550 and the 2620 cannot directly route traffic between the two networks. In addition to this we would like to remove the internet T-1 in building B and route all their internet traffic through the building to building T-1 and out our 10meg internet connection.
Can anyone provide any advice that doesn't involve a really convoluted routing system and doesn't involve subnetting our class C? If the 2620's could simply act as bridges that would be great, I don't want to invest a whole lot of time in this since in a few months we will have a DS3 in place between the buildings and will be bridging accross that.