This is basically a shot in the dark. I have worked with many VoIP phones in the past, but not NEC phones. I'm not an NEC tech, but in this case, we are doing sub work for an NEC dealership.

Short version, I connected an NEC phone to a Cisco POE switch. After a few minutes, the Cisco switch rebooted. A few minutes after that it reboots again. Moved to a non-POE Cisco switch (same model) with a POE injector, same results.

IT's "just tell them something" answer is that it is an IP conflict. I doubt it. Same results 2 switches on 2 different networks. Dealer says that they talked to NEC support, and there are no known conflicts with Cisco switches. I asked another CIsco tech. He never heard of this before.

Before you say Broadcast Storm, I did not loop the connections. I only connected the LAN port, not the PC side.

I am not sure of the NEC phone model. I think that the NEC system is an SV9100

I have a Netgear switch in my truck when I go out today, but just curious if anyone has ever heard of anything like this. I have never heard of an IP device causing a switch to reboot like this before.