Allied Telesis AT-x220-28GS Installation Manual page 54

Chapter 3: Troubleshooting
46
Verify that the correct type of fiber optic cabling is being used.

Verify that the port is connected to the correct fiber optic cable.

This is to eliminate the possibility that the port is connected to the
wrong remote network device, such as a powered off device.
Try connecting another network device to the fiber optic port using

a different cable. If the port is able to establish a link, then the
problem is with the cable or with the other network device.
Use the switch's management software to verify that the port is

enabled.
If the remote network device is a management device, use its

management firmware to determine whether its port is enabled.
Test the attenuation on the fiber optic cable with a fiber optic tester

to determine whether the optical signal is too weak (sensitivity) or
too strong (maximum input power).
Problem 4: The switch functions intermittently.
Solutions: Check the system hardware status through the management
software:
Use the show system environment command in the Privileged

Exec mode to verify that the input voltage from the power source to
the switch is stable and within the approved operating range. The
unit will shut down if the input voltage fluctuates above or below
the approved operating range.
Use the show system environment command in the Privileged

Exec mode to verify that the fan is operating correctly.
Verify that the location of the switch allows for adequate airflow.

The unit will shut down if it is in danger of overheating.
Problem 5: A port's Link/Activity/Speed LED is blinking.
Solutions: The link between the port and the network device is
intermittent. Try the following:
Connect another network device with a different cable to the port. If

the Link LED remains steady on, then the problem is with the
original cable or the network device.
If the problem is with an SFP transceiver, check that the

transceiver is fully inserted in the slot.