Cisco ASR 1000

20-10
Cisco ASR 1000 Series Aggregation Services Routers SIP and SPA Software Configuration Guide
OL-14127-08
Chapter 20 Troubleshooting the Serial SPAs
Performing Basic Interface Troubleshooting
Symptom: Increasing number of input errors in excess of 1 percent of total interface traffic
Serial Lines: Troubleshooting Serial Line Input Errors
Table 20-5 describes the various types of input errors displayed by the show interfaces serial command,
possible problems that might be causing the errors, and solutions to those problems.
Ta b l e 20-4 Serial Lines: Increasing Input Errors in Excess of 1 Percent of Total Interface Traffic
Possible Problem Solution
The following problems
can result in this
symptom:
• Faulty telephone
company equipment
• Noisy serial line
• Incorrect clocking
configuration
• Incorrect cable or
cable that is too long
• Bad cable or
connection
• Bad CSU or DSU
• Bad router hardware
• Data converter or
other device being
used between router
and DSU
Note We strongly recommend against the use of data converters when
you are connecting a router to a WAN or a serial network.
1. Use a serial analyzer to isolate the source of the input errors. If you
detect errors, there likely is a hardware problem or a clock mismatch
in a device that is external to the router.
2. Use the loopback and ping tests to isolate the specific problem source.
3. Look for patterns. For example, if errors occur at a consistent interval,
they could be related to a periodic function, such as the sending of
routing updates.