Allied Telesis AT-MC103ST/FS3, FS4 - Manual (Page 14)

4
Link Test/MissingLink Button
The Link Test/MissingLink button allows you to perform a link test on the
ports on the media converter. This button also allows you to activate the
MissingLink feature on the unit. Both features are describe in the following
section.
Link Test. The link test is a fast and easy way for you to test the connections
between the ports on the media converter and the 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 be able to focus on the
fiber optic cable and node where the problem resides.
A link test is performed when the button is in the LNK TST (OUT) position.
For instructions on performing a link test, refer to “Testing the Installation”
on page 13.
Note
Performing a link test does not interfere with a media converter’s ability
to pass network traffic.
MissingLink. The MissingLink feature enables the fiber optic ports on the
media converter to pass the “Link” status of their connections to each other.
When the media converter detects a problem with one of the ports, such as the
loss of connection to a node, the media converter shuts down the connection to
the other port, thus notifying the node that the connection has been lost.
For example, if the network twisted pair cable to the 100Base-TX port on the
media converter were to fail, the media converter would respond by dropping
the link on the 100Base-FX fiber optic port. In this way, the media 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 hubs and switches 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 node or send out a trap to a network
management station, and so alert the network administrator of the problem.
Note
The MissingLink feature is disabled when you perform a link test with
the Link Test/MissingLink button. Consequently, to ensure that the
MissingLink feature is activated on the media converter, always set the
button to the M/L ON (IN) position during normal network operations.