RAS Clients receive different IPs from D

I have an SBS 4 Network set up, and for RAS, I have one modem dialing out to my ISP.
The other Modems are on a Cisco 2500 series router and are for receiving Remote Access calls only. The problem I am having is, the remote clients receive a “No Domain server” message but logs in. With this I cannot browse my network.(I am using TCP/IP and Netbuei protocols) I run winipcfg on the remote client and I realised that the IP it received is from the ISP but not my Local address. Any ideas on how the remote clients can browse the LAN and use proxy on server??