Information Technology Reference
In-Depth Information
•
SABMs
—Number of set asynchronous balance mode requests
•
RNRs
—Number of receiver not ready events
•
FRMRs
—Number of protocol frame errors
•
RESTARTs
—Number of restarts
•
DISCs
—Number of disconnects
All but the RESTARTs count are LAPB events. Because X.25 requires a stable data link, LAPB problems
commonly cause an X.25 restart event that implicitly clears all virtual connections. If unexplained X.25
restarts occur, examine the underlying LAPB connection for problems. Use the
debug lapb
exec
command to display all traffic for interfaces using LAPB encapsulation. The no form of this command
disables debugging output:
[no] debug lapb
The
[no] debug lapb
command displays information on the X.25 Layer 2 protocol. It is useful to users
who are familiar with LAPB. You can use the
debug lapb
command to determine why X.25 interfaces
or LAPB connections are going up and down. It is also useful for identifying link problems, as evidenced
when the
show interfaces
command displays a large number of rejects or frame errors over the X.25
link.
Caution
Exercise care when using
debug
commands. Many
debug
commands are
processor-intensive and can cause serious network problems (such as degraded
performance or loss of connectivity) if they are enabled on an already heavily loaded router.
When you finish using a
debug
command, remember to disable it with its specific
no debug
command (or use the
no debug all
command to turn off all debugging).
Figure 19-6 shows the output of the X.25 version of the
show interfaces serial
exec command and
indicates the important fields.
