Allied Telesis AT-FS238b/2 - Manual (Page 25)

AT-FS238a/x and AT-FS238b/x Series Installation Guide
15
Mode Selection Button
Link Test
The link test is a fast and easy way for you to test the connections between the
bridging converter ports and the end-nodes that are connected to the ports. If
a network problem occurs, you can perform a link test to determine which port
is experiencing a problem, and so be able to focus your troubleshooting efforts
on the cable and end-node where the problem resides.
To perform a link test, toggle the Mode Selection button until the LT LED is
green. The LNK LEDs for the ports should now be green, indicating that they
were able to establish a link with their end-nodes. If a LNK LED is off, the
port could not establish a link. Refer to “Troubleshooting” on page 33 for
suggestions on how to remedy the problem.
Note
Performing a link test does not interfere with a bridging converter’s
ability to pass network traffic.
MissingLink
The MissingLink feature enables the ports on the bridging converter to pass
the “Link” status of their connections to each other. When the bridging
converter detects a problem on one of the ports, such as the loss of connection
to an end-node, the bridging converter shuts down the connection to the other
port, thus notifying the end-node that the connection has been lost.
For example, if the twisted pair cable to the 10Base-T/100Base-TX port on the
bridging converter were to fail, the unit would respond by dropping the link on
the 100Base-FX fiber optic port. In this way, the bridging converter notifies
the end-node connected to the fiber optic port that the connection on the
twisted pair port has been lost. If the failure had started with the fiber optic
cabling, the unit would drop the link to the twisted pair port.
The value to this type of network monitoring and fault notification is that
some devices can be configured to take a specific action in the event of the loss
of connection on a port. In some cases, the unit can be configured to seek a
redundant path to a disconnected end-node or send out a trap to a network
management station, and so alert the network administrator of the problem.