Hello there - I'm new to this forum so am hoping you guys can help me out of a hole!!
I've inherited a Windows 2003 Active Directory domain that has got a single DHCP server on the network, about 20 HP Switches and about three hundred client pcs. The previous IT Manager set it up with a subnet mask of 255.255.252.0 and a single scope of 10.12.12.2 - 10.12.15.44 with a lease period of 14 days.
What happens is every 7 days or so, a number of PCs (that are all connected to the same switch) do their job and go and seek out the DHCP server to verify their address and to renew but they all lose their network connections - my helpdesk phone rings off its hook with users complaining! The other IT staff have been told that when this happens the "quick way" of fixing it is to reset the switch that all the PCs are connected to and this does fix the problem. When I check out the event logs on the affected PCs they all report issues with renewing IP addresses.
I have not seen this problem before and I have not seen a single scope setup in this way before. What do you guys think? I think I should have at least one other DHCP server on the network for redundancy anyway. Should I have multiple scopes setup for four network segments (e.g. 10.12.12.x 10.12.13.x 10.12.14.x and 10.12.15.x) on the one server?
I agree it looks like a hardware problem. Does it happen to the same computers or random ones.
We had something similar once when the onboard network card mac address where the same as other computers on the network.
The reason I thought it might be DHCP server related is I have a number of switches and this problem has happened on quite a few of them. When I check the event logs on the switches there is nothing recorded - they just report system up time (expect of course when the switch is reset!) In the past we have even had the switch management software open when the "issue" occurs and nothing is reported in the logs.
The client PCs all record DHCP problems - and they all occur at 50% through the lease period - it just seemed to much of a coincidence that the switch goes down when the client are trying to renew?
Sounds like the switch might be stopping what it thinks is a broadcast storm.
You might be onto something there, but I've never known a switch to treat DHCP requests as a broadcast storm. It's probably more likely one of the machines has a faulty network adapter and is creating the broadcast storm.
I've seen it happen before on HP switches and all LEDs are on permanently.