Information Technology Reference
In-Depth Information
1.
ESF = Extended Superframe Format
2.
B8ZS = binary eight-zero substitution
Serial Lines: Increasing Interface Resets on Serial Link
Interface resets that appear in the output of the show interfaces serial exec command (see Figure 15-1)
are the result of missed keepalive packets.
Symptom: Increasing interface resets on serial link
Table 15-6 outlines the possible problems that might cause this symptom and describes solutions to those
problems.
Table15-6 Serial Lines: Increasing Interface Resets on Serial Link
Possible Problem
Solution
The following
problems can
result in this
symptom:
When interface resets are occurring, examine other fields of the
show interfaces serial command output to determine the source
of the problem. Assuming that an increase in interface resets is
being recorded, examine the following fields:
Congestion
on link
(typically
associated
with output
drops)
If there is a high number of output drops in the show
interfaces serial output, see the section “Serial Lines:
Increasing Output Drops on Serial Link,” earlier in this
chapter.
1.
Check the Carrier Transitions field in the show interfaces
serial display. If carrier transitions are high while interface
resets are being registered, the problem is likely to be a bad
link or a bad CSU or DSU. Contact your leased-line or
carrier service, and swap faulty equipment, as necessary.
2.
Bad line
causing CD
transitions
Possible
hardware
problem at
the CSU,
DSU, or
switch
Examine the Input Errors field in the show interfaces serial
display. If input errors are high while interface resets are
increasing, the problem is probably a bad link or a bad
CSU/DSU. Contact your leased-line or other carrier service,
and swap faulty equipment, as necessary.
3.
Serial Lines: Increasing Carrier Transitions Count on Serial Link
Carrier transitions appear in the output of the show interfaces serial exec command whenever there is
an interruption in the carrier signal (such as an interface reset at the remote end of a link).
Symptom: Increasing carrier transitions count on serial link
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