Cisco Catalyst 3750-E Series, Software Configuration Manual

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Catalyst 3750-E and 3560-E Switch Software Configuration Guide
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Chapter 49 Troubleshooting
Troubleshooting Tables
No PoE on all ports or a group of ports.
Trouble is on all switch ports. Nonpowered
Ethernet devices cannot establish an Ethernet
link on any port, and PoE devices do not
power on.
If there is a continuous, intermittent, or reoccurring alarm related to
power, replace the power supply if possible it is a field-replaceable unit.
Otherwise, replace the switch.
If the problem is on a consecutive group of ports but not all ports, the
power supply is probably not defective, and the problem could be related
to PoE regulators in the switch.
Use the show log privileged EXEC command to review alarms or system
messages that previously reported PoE conditions or status changes.
If there are no alarms, use the show interface status command to verify
that the ports are not shut down or error-disabled. If ports are
error-disabled, use the
shut and no shut interface configuration
commands to re-enable the ports.
Use the sh ow env power and show power inline privileged EXEC
commands to review the PoE status and power budget (available PoE).
Review the running configuration to verify that power inline never is
not configured on the ports.
Connect a nonpowered Ethernet device directly to a switch port. Use
only a short patch cord. Do not use the existing distribution cables. Enter
the
shut and no shut interface configuration commands, and verify that
an Ethernet link is established. If this connection is good, use a short
patch cord to connect a powered device to this port and verify that it
powers on. If the device powers on, verify that all intermediate patch
panels are correctly connected.
Disconnect all but one of the Ethernet cables from switch ports. Using
a short patch cord, connect a powered device to only one PoE port.
Verify the powered device does not require more power than can be
delivered by the switch port.
Use the show power inline privileged EXEC command to verify that the
powered device can receive power when the port is not shut down.
Alternatively, watch the powered device to verify that it powers on.
If a powered device can power on when only one powered device is
connected to the switch, enter the
shut and no shut interface
configuration commands on the remaining ports, and then reconnect the
Ethernet cables one at a time to the switch PoE ports. Use the
show
interface status and show power inline privileged EXEC commands to
monitor inline power statistics and port status.
If there is still no PoE at any port, a fuse might be open in the PoE
section of the power supply. This normally produces an alarm Check the
log again for alarms reported earlier by system messages.
For more information, see No PoE On Any Port or a Group of Ports on
Cisco.com.
Figure 49-1 Power Over Ethernet Troubleshooting Scenarios (continued)
Symptom or problem Possible cause and solution