Cisco ASR 1000 Configuration Guide

20-7
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
Serial Lines: Increasing Output Drops on Serial Link
Output drops appear in the output of the show interfaces serial command when the system is attempting
to hand off a packet to a transmit buffer but no buffers are available.
Symptom: Increasing output drops on serial link
Table 20-2 outlines the possible problem that might cause this symptom and describes solutions to that
problem.
Serial x is up, line
protocol is down
(disabled)
A high error rate has
occurred due to a remote
device problem.
A CSU or DSU hardware
problem has occurred.
Router hardware (interface)
is bad.
1. Troubleshoot the line with a serial analyzer and
breakout box.

Examine the output of 
show controller T1 or 
show controller T3 or 
show controller serial x depending on whether
the SPA is an 8-Port Channelized T1/E1 SPA,
4-Port Channelized T3 SPA, or 4-Port Clear
Channel T3/E3 SPA.
2. Loop CSU/DSU (DTE loop). If the problem
continues, it is likely that there is a hardware
problem. If the problem does not continue, it is
likely that there is a telephone company
problem.
3. Swap out bad hardware, as required (CSU,
DSU, switch, local or remote router).
Serial x is
administratively
down, line
protocol is down
The router configuration
includes the shutdown
interface configuration
command.
A duplicate IP address exists.
1. Check the router configuration for the
shutdown command.
2. Use the no shutdown interface configuration
command to remove the shutdown command.
3. Verify that there are no identical IP addresses
using the show running-config privileged
EXEC command or the show interfaces EXEC
command.
4. If there are duplicate addresses, resolve the
conflict by changing one of the IP addresses.
Table 20-1 Serial Lines: show interfaces serial Status Line Conditions (continued)
Status Line 
Condition Possible Problem Solution

Cisco ASR 1000 Specifications

General

Brand	Cisco
Model	ASR 1000
Category	Network Router
Language	English