Cisco Catalyst 2975 Software Configuration Manual page 885

Chapter 38 Troubleshooting
Figure 38-1 Power Over Ethernet Troubleshooting Scenarios (continued)
Symptom or problem
Cisco IP Phone disconnects or resets.
After working normally, a Cisco phone or
wireless access point intermittently
reloads or disconnects from PoE.
Non-Cisco powered device does not work
on Cisco PoE switch.
A non-Cisco powered device is connected
to a Cisco PoE switch, but never powers on
or powers on and then quickly powers off.
Non-PoE devices work normally.
OL-19720-02
Possible cause and solution
Verify all electrical connections from the switch to the powered device. Any
unreliable connection results in power interruptions and irregular powered device
functioning such as erratic powered device disconnects and reloads.
Verify that the cable length is not more than 100 meters from the switch port to
the powered device.
Notice what changes in the electrical environment at the switch location or what
happens at the powered device when the disconnect occurs?
Notice whether any error messages appear at the same time a disconnect occurs.
Use the show log privileged EXEC command to review error messages.
Verify that an IP phone is not losing access to the Call Manager immediately
before the reload occurs. (It might be a network problem and not a PoE problem.)
Replace the powered device with a non-PoE device, and verify that the device
works correctly. If a non-PoE device has link problems or a high error rate, the
problem might be an unreliable cable connection between the switch port and the
powered device.
For more information, see
Use the show power inline command to verify that the switch power budget
(available PoE) is not depleted before or after the powered device is connected.
Verify that sufficient power is available for the powered device type before you
connect it.
Use the show interface status command to verify that the switch detects the
connected powered device.
Use the show log command to review system messages that reported an
overcurrent condition on the port. Identify the symptom precisely: Does the
powered device initially power on, but then disconnect? If so, the problem might
be an initial surge-in (or inrush) current that exceeds a current-limit threshold for
the port.
For more information, see
Switch on Cisco.com.
Cisco Phone Disconnects or Resets
Non-Cisco PD Does Not Work Correctly on Cisco PoE
Catalyst 2975 Switch Software Configuration Guide
Troubleshooting Tables
on Cisco.com.
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