Cisco Catalyst 2960 Series, Configuration Manual

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Possible Cause and Solution Symptom or Problem
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.
Cisco IP Phone disconnects or resets.
After working normally, a Cisco phone
or wireless access point intermittently
reloads or disconnects from PoE.
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.
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.
Related Topics
Power over Ethernet Ports, on page 1626
Configuration Examples for Troubleshooting Software
Example: Pinging an IP Host
This example shows how to ping an IP host:
Switch# ping 172.20.52.3
Consolidated Platform Configuration Guide, Cisco IOS Release 15.2(4)E (Catalyst 2960-X Switches)
1652
Configuration Examples for Troubleshooting Software