[cisco-voip] Strike 2 - Dead 7940G IP Phones

[Micah Bennett]

Waiting on my network admin to get in so I thought I would send this out
and see if anyone has seen this before.

Tuesday morning 3:00am, a single IP phone (out of 200) on our network
(being used by the single call center agent on that shift) loses
connection to the network and shows "Ethernet Disconnected" on the phone
screen.

We are using Cisco 3560 switches for our user network with POE from the
switch.  Ethernet cable from the wall to the phone and from the phone to
the PC.  

Did not think much about it at that time, just figured it was a bad
phone.  First one since our deployment last July.  I replaced the phone
with a spare and sent the bad one back to Cisco under RMA.

In testing the bad phone, it seems that the internal network switch is
completely dead.  After the initial failure it showed "Ethernet
Disconnected" on the screen so it was still getting POE from the switch.
When disconnected and moved to another network port, it will not come
back on with POE.  I had to use a power cord to supply power and the
phone still shows "Ethernet Disconnected".

Everything was fine all day Tuesday, and Wednesday.

Thursday morning, 3:00am, exact same problem on exact same network port,
killing the replacement phone that was installed on Tuesday.  Everything
is exactly the same even down to the time of failure.  Phone exhibits
the exact same symptoms.  Was responding to POE but showing Ethernet
Disconnected until disconnected from the network.  After disconnection,
the unit only responds to power from a cord, and not POE.  Still shows
Enet Disconnected.

Is the POE coming from the switch on this port killing the phone?  Has
anyone seen anything like this before?

Right now that station does not have a phone.  I don't want to burn up a
third one. 

Micah Bennett
Telecommunications Admin
Automated License Systems

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