I have a Novel bases network running NT workstations. I recently isntalled several switches to help reduce network traffic. After installing the switches, about 15% of my NT Workstation clients can no longer get an IP address. They get Semaphore errors in Event viewer. I have tried reloading drivers, service packs everything. Some of my PC's have SP3 and they work, others don't, some have SP6a, some work, others don't. I have yet to get one of these PC's working. I have NO NT servers, it is completely Novell in the background. If I move the PC's to the same subnet as the DHCP server, THEY WORK, but once moved back to their subnet, they fail. (The PC right next to it works fine, but it fails) Rebuilding the PC's doesn't work either. (When I installed the switches, I made each switch a seperate subnet and then added the subnets into the DHCP server) If anyone has any quick thoughts, let me know. Please email me as soon as possible.

The fact that they work when in the same subnet as the DHCP server and that you have installed new switches, would indicate to me that the default gateway on the machines is wrong

I recently converted from Token Ring to Ethernet and had the same problem. NT for some reason cannot or will not span the subnet. You will need to setup WINS or use a host file to point to the servers. I would suggest WINS. I agree that the gateway could also be wrong. If it is wrong, the machines will not find the router. But, if all are internal and the server internal, you should not be hitting the router to find your servers anyway. If you are, you are wasting time with net traffic. If you are changing the subnet on your network, you can setup a second NIC in your server to allow the NT's that you have not changed the IP on to use until you get to all of the machines. This would allow all machines to continue to interface with the servers until you finish your install.

getting an ip from a dhcp server is done via broadcast - which doesn't go across subnets ie non-routable. you should set up dhcp relay on a machine an each subnet or use a routing table.