Recently had a problem with a DHCP server no leasing out DHCP address randomly. Restarting the service would not fix this , the only thing that would bring it back would be a server restart.

The last entry in the log files would be a Renew. The DHCP database looked fine. There was a DHCP Memory leak in the event log.

The server assigned address for over 1500 Clients , however it was using the E1000 Adapter , once we changed this to VMXNET 3 it resolved the issue