We had a very strange situation crop up on our network the other day. Phones started hanging when their DHCP leases expired. We put a packet sniffer on the network and discovered that DHCP requests from the phones would be answered not only by our legitimate DHCP servers (infoblox appliances) but also by the Unity server. However, the offer and ACK from the Unity server contained 0.0.0.0 as an issued IP address and it would arrive at the phone first and thus, the phone would get stuck without an IP address. This didn't affect phones which were renewing their leases before the expiration because that traffic was directed (not broadcast). We were able to resolve this simply by disabling the NIC on the Unity server and then re-enabling it. But this behavior seems very odd. The Unity server is not running a DHCP server as far as we can tell. Is Unity supposed to have this capability built into any of the Unity services? We can't seem to reproduce the behavior now.