I’ve got a Grandstream GXP-2000 VOIP phone, which is ordinarily pretty good, but today my DHCP server went offline, and trying to bring it back was a problem because something else was using its static address.
The culprit? The phone. It had assigned itself the IP of its DHCP server and wasn’t responding to pings. I had to do a TCP dump and arping it to find the bugger. Unplug the phone, the DHCP server comes right back, then plug the phone in, and it gets its address per usual.
Bad phone, bad!