Question : how do i connect to a domain on a different network

I have set up two networks, on eperimeter and one internal network. I have an isa firewall separating the networks. My domain controller is in the perimeter network. can I connect to the domain from the internal network and if so how do I do it? if i cant do I need to split my network into sub networks to achieve a single domain controlled network?

Answer : how do i connect to a domain on a different network

Some more questions -
Can all of the machines ping the other machines on their network?
   - If this is the case, we know that we have a properly configured network.  If not then
     we have some TCP/IP issues.

Can all of the machines resolve to proper ip address on their own side?
     - If  not then they are never going to resolve names on the other network.

Are you running your own name server?
     - This may be something to consider?

I forgot to ask if the machines on the internal network, can ping the router on the perimeter network.  "Duh" - I just realized something.  If your Internal network is 192.168.1.x and your external network is 192.168.0.x; where is your gateway?   What is the subnet that you are using?  So let me probe a little deeper.... What version of windows are you using?  

If your IP address is 192.168.1.1 and your subnet is 255.255.255.0; then  the "world" according to that machine, consists 192.168.1.1 to 192.168.1.254.  You will not be able to see anything else without a gateway.  Your gateway will have something that both machines can see.  Do machines on either network access the internet?  If so how are they accessing the internet?  

I recently put a lab in a private school, running stictly windows XP, no domain controller.  I wanted to enable the Staff to see all the machines, but the students not to be able to see anything but the lab.  (There is a xp machine in the lab to act as a server).

The staff machines are 192.168.1.150 to 192.168.1.200 with a subnet mask of 255.255.255.0.  The lab  machines are 192.168.1.1 to 192.168.1.120 with a subnet of 255.255.255.128.  The lab's world is 192.168.1.1 to 192.168.1.126 (I think, may not  be exact).  The lab server is 192.168.1.120; and the router (and gateway) for the internet is 192.168.1.100.

This way, the staff can see the lab machine to post lab assignments.  The staff can see the router to access the net.  The students can see the router to access the net, The students can see the lab server to print, and get lab assignments.  However, the lab can't see the teacher machines.  They did not want to go with a 2003 setup with a domain controller.

I am suspecting that we have an issue here where we have not logical connection between the two networks.  You might consider, changing your IP subnetting scheme so that the machines can see the domain controller, but not see each other.

Let me know if I can be of any more assistance.