Cabletron Systems SPECTRUM, User Manual

Page: 74 / 150

FDDI Management
4-6 Port Configuration
Viewing the FDDI Port Chart
To view the FDDI Port Chart window, highlight an entry in the scroll list and click
. The FDDI Port Chart window, Figure 4-3 , will appear.
Figure 4-3. FDDI Port Chart Window
The FDDI Port Chart window displays the following information about the
selected port or ports, in both numeric and graphical format:
LEM Count
The LEM (Link Error Monitor) Count displays the number of times each port’s
Link Error Monitor has detected a link error. A link error occurs when a port’s line
state goes from Idle to Unknown and remains there for at least 80 ns, or when the
line state goes from Active to Unknown and remains there for at least 320 ns. A
growing LEM Count usually indicates a physical problem with the connectors or
the cable between a port and the node at the other end of its cable segment. If you
can wiggle the cable and watch the LEM Count increase, you know you have a
faulty cable or connector. Dirt or film on the connector cable ends can also add to
the LEM Count.
LEM Reject Count
The number of times the port’s link has exceeded the configured LER Cutoff level
and been removed as faulty (disabled by station management). SMT
automatically re-enables a port when the error rate falls below the cutoff value.
See Alarm Configuration,
page 4-9 , for more information on setting the LER
Cutoff threshold.