Allied Telesis AlliedWare Plus GS980MX Series Installation Manual page 240

Chapter 11: Troubleshooting
240
Problem 3: A twisted pair port on the switch is connected to an active
network device but the port's LINK/ACT LED is off.
Solutions: The port is unable to establish a link to a network device. Try
the following:
Verify that the network device connected to the twisted pair port is

powered on and is operating properly.
Try connecting another network device to the twisted pair port with

a different cable. If the twisted pair port is able to establish a link,
then the problem is with the cable or the other network device.
Verify that the twisted pair cable does not exceed 100 meters

(328 feet).
Verify that you are using the appropriate category of twisted pair

cable. Refer to "Cable Requirements" on page 34.
Verify that the port is connected to the correct twisted pair cable.

Note
Twisted pair ports may require five to ten seconds to establish a link.
Problem 4: The LINK/ACT LED for an SFP or SFP+ transceiver is off.
Solutions: The fiber optic port on the transceiver is unable to establish a
link to a network device. Try the following:
Verify that the remote network device connected to the fiber optic

port is operating properly.
Verify that the fiber optic cable is securely connected to the port on

the transceiver and to the port on the remote network device.
Check that the transceiver is fully inserted in the port.

Verify that the operating specifications of the fiber optic ports on

the transceiver and remote network device are compatible.
Verify that the correct type of fiber optic cabling is being used.

Verify that the port is connected to the correct fiber optic cable.

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 managed device, use its

management firmware to determine whether its port is enabled.
Test the attenuation of both directions 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).