machines on Linksys router cant c domain

Hi,

I have some users that bought a Linksys router(4 port cheapie). They put all their machines behind the router that acts as a firewall. These machines are part of a Windows NT domain, but now that they are behind the router they can’t see the domain. The router support port forwarding. What type of traffic do I have to allow thru the router so the machines can see the domain?

We have HP4000/8000 that support VLAN’s. Are there any tricks I can play w/ that? Should I just tell themto get a firewall?

Please help, it’s a rush.