Cisco Systems 3560 Manual De Usuario

Cisco IP Phone disconnects or resets.

After working normally, a Cisco phone or 
wireless access point intermittently reloads or 
disconnects from PoE.

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 

Cisco Phone Disconnects or Resets

 on 

Cisco.com.

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. 

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

 Non-Cisco PD Does Not Work Correctly

 

on 

Cisco PoE Switch

 on Cisco.com.