Subnets

I have a domain and lan setup for our site. We are part of a much larger wan. I have a remote site with a T1 connecting the 2 sites. Say our domain is XXX.xxx.XX3.0 with a gateway of XXX.XXX.XX3.1 and a mask of 255.255.255.0 I was told that the routers at the couldn’t be in the same ip group so the one at the remote site was setup as XXX.XXX.XX2.129 and the workstations were set to XXX.XXX.XX2.130 thru 145 Although this works it keeps giving me little problems that I believe would go away if the subnet could be part of our block of IPs so my question is: do both routers have to be part of different subnets?