Allied Telesis AT-S102 - Manual (Page 52)

Chapter 2: AT-CM and AT-CV Media Converter Line Cards
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The same would happen if the twisted pair port on the line card in the
AT-CV5000 Chassis did not have a link with its device. The fiber optic link
across the line cards would be unavailable.
This relationship between OAM on the fiber optic port and the state of the
link on a twisted pair port has to be taken into account when using this
operating mode. You must remember that in order for OAM and the OAM-
based features to work on a line card set to this operating mode, there
have to be links on both ports on the line card, and not just on the fiber
optic port. If you want to have access to OAM even when there is no link
on a twisted pair port on the line card, you should use the Link Test and
OAM operating mode instead.
Smart
MissingLink
Mode
This mode, which is supported on all of the media converter line cards, is
nearly identical to the MissingLink mode. It, too, lets the two ports on a
media converter line card share the link status of their network
connections. The difference is that this mode does not completely shut off
the transmitter of a port when a companion port on the line card loses or
cannot establish a link to a network device. Rather, it pulses the port’s
transmitter and flashes the port’s Link LED once a second to signal that
the port can still establish a link to its network device and that the link loss
originated on the companion port on the line card.
When the connection is reestablished on a port, the companion port
automatically resumes normal operations to permit the two ports to
forward traffic again.
The advantage of the Smart MissingLink mode over the MissingLink mode
is that troubleshooting network problems is easier because you can use
the Link LEDs. For example, assume that the fiber optic port on a media
converter line card set to the Missing Link mode did not have a link to its
network device. The mode’s response would be to disable the transmitter
on the companion port, the twisted pair port. The result would be that the
Link LEDs for both ports would be off, making it difficult for you to
determine which port experienced the original link loss.
In contrast, the Smart MissingLink mode would respond by pulsing the
transmitter on the twisted pair port and flashing the port’s Link LED about
once a second, to signal that the failure originated on the fiber optic port.
The behavior of the operating mode is the same regardless of which port
does not have a link. In the previous example, the loss was on the fiber
optic port. But if the loss happened on the twisted pair port, the mode
pulses the transmitter and the Link LED for the fiber optic port.
As with the other operating modes, this mode does not interfere with the
flow of network traffic through the ports of a line card during normal
network operations of a media converter line card. However, Allied Telesis
recommends limiting its use to diagnosing link failures, particularly if the
network devices connected to the ports are managed devices. The pulsing