We have done some reconfiguration of our school network and we are now having DHCP issues. I'm hoping someone here can help me out. I have run the issue through Microsoft Technical support and they tell me that the issue is with the switch configuration, but I'm not sure what to change.
We have a Windows 2008 DHCP server and several other network devices and servers all on one subnet and have now moved our Windows clients onto a separate subnet. All are at the same physical location and VLAN and connect directly to the PC-6024. We also have three other physical sites, each of which also have their own PC-6024 and connect to the main site PC-6024 via fiber/GBIC.
All of the PC-6024's have DHCP Relay enabled and direct DHCP requests to a single DHCP server at the main site. DHCP relay is working great at the remote sites. The problem is at the main site.
The Problem: When a Windows client sends out a request for a DHCP address, the DHCP server is receiving two requests. One request is coming via the DHCP Relay agent on the switch and the other is going directly to the DHCP server. The DHCP server receives the first request, sends and ACK back to the client and then rejects the second request, with an error message stating that the IP address is already in use. The end result is that the Windows client never gets an IP address, which of course means it can't connect to the network.
Microsoft's analysts tell me that the DHCP server should only be receiving the DHCP request from the PC-6024's DHCP Relay Agen because the DHCP server is on a different subnet. They tell me that we need to figure out how to tell the switch NOT allow the DHCP broadcasts through to the DHCP server.
The DHCP server is run on a Domain controller, and moving that domain controller to the same subnet as the Windows clients is not an option. I have tried turning of DHCP Relay on the main PC-6024, when I do that, DHCP relay requests from the remote sites don't get through.
I could potentially move just the DHCP service to a separate server, but I would prefer to find the appropriate setting on the switch rather than firing up a new server just to handle DHCP requests and the MS analyst is not certain that will solve the issue.
Any help with this issue would be greatly appreciated!
Thanks,
Mark