For a few weeks now, we have started having issues with workstations losing their connections to the lan. When it happens, the workstation seems to lose it's ip address. If I simply unplug the network connection from the computer and plug it back it, the problem is fixed. Dhcp assigns an IP and everything works again but I can't figure out why it's happening.
General network structure is like this. A Windows domain controller gives out dhcp addresses and is connected to a Central Server Switch. Workstations are connected to a cisco ip phone which is then connected to a Central Workstation Cisco 3560 Switch. Then the Server switch and Workstation Switches all connect to another 3560 switch which is the central layer 3 switch / router for the lan. The workstations, Phones, and Servers are all in their own Vlans. POE active for phones, spanning tree turned off, dhcp helper address setup on the main layer 3 switch. I can send cisco config if you think it could help.
The problem only seems to occur on a select group of workstations in one section of the office but those workstations that lose their ip addresses are sometimes on different switches. I have swapped out the central layer 3 switch and that didn't help.
I am proficient in cisco and windows networking but can't seem to find the answer so looking for an expert to throw out some magic to try.