Troubleshooting Power Over Ethernet (Poe) - Cisco Catalyst 2975 Software Configuration Manual

Chapter 38 Troubleshooting

Troubleshooting Power over Ethernet (PoE)

Figure 38-1 Power Over Ethernet Troubleshooting Scenarios
Symptom or problem
No PoE on only one port.
Trouble is on only one switch port. PoE
and non-PoE devices do not work on this
port, but do on other ports.
OL-19720-02
Possible cause and solution
Verify that the powered device works on another PoE port.
Use the show run, show interface status, or show power inline detail user
EXEC commands to verify that the port is not shut down or error disabled.
Most switches turn off port power when the port is shut down, even
Note
though the IEEE specifications make this optional.
Verify that the Ethernet cable from the powered device to the switch port is good:
Connect a known good non-PoE Ethernet device to the Ethernet cable, and make
sure that the powered device establishes a link and exchanges traffic with another
host.
Verify that the total cable length from the switch front panel to the powered
device is not more than 100 meters.
Disconnect the Ethernet cable from the switch port. Use a short Ethernet cable to
connect a known good Ethernet device directly to this port on the switch front
panel (not on a patch panel). Verify that it can establish an Ethernet link and
exchange traffic with another host, or ping the port VLAN SVI. Next, connect a
powered device to this port, and verify that it powers on.
If a powered device does not power on when connected with a patch cord to the
switch port, compare the total number of connected powered devices to the switch
power budget (available PoE). Use the show inline power and show inline
power detail commands to verify the amount of available power.
For more information, see No PoE On One Port on Cisco.com.
Catalyst 2975 Switch Software Configuration Guide
Troubleshooting Tables
38-27