Allied Telesis AT-MC303 - Manual (Page 14)

4
MissingLink/Link Test Button
The MissingLink/Link Test (M/L ON/LNK TST) 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. A link test is a fast and easy way for you to test the integrity of the
connections to the two ports on the media converter. The test determines
whether the ports are receiving a valid signal from the end nodes connected to
the ports. This test is typically used after installation to verify that the unit
and connections are operating properly, or whenever you need to test the ports
or the integrity of the connections to the nodes connected to the ports. The
section “Verifying the Installation” on page 15 contains instructions on how to
perform a link test.
Note
Leaving the MissingLink/Link Test button in the Link Test position will
not affect the operation of the media converter during normal network
operations. However, the MissingLink feature of the media converter is
disabled when the button is in the Link Test position.
MissingLink. The MissingLink feature enables the twisted pair port and the
fiber optic port 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 device shuts down
the connection to the other port, thus notifying the node that the connection
has been lost.
For example, if the 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.
In the example, once the end node connected to the fiber optic port has
realized that the connection to the end node on the twisted pair port has been
lost on the media converter, the end node can send a trap to the management
station, alerting the network administrator of the problem, or attempt to
establish a redundant path to the disconnected node.