Serial Lines: Increasing Output Drops On Serial Link - Cisco ASR 1000 Configuration Manual

Chapter 20 Troubleshooting the Serial SPAs
Table 20-1
Status Line 
Condition
Serial x is up, line
protocol is down
(disabled)
Serial x is
administratively
down, line
protocol is down

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
problem.
OL-14127-08
Serial Lines: show interfaces serial Status Line Conditions (continued)
Possible Problem
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.
The router configuration
includes the shutdown
interface configuration
command.
A duplicate IP address exists.
outlines the possible problem that might cause this symptom and describes solutions to that
Cisco ASR 1000 Series Aggregation Services Routers SIP and SPA Software Configuration Guide
Performing Basic Interface Troubleshooting
Solution
Troubleshoot the line with a serial analyzer and
1.
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.
Loop CSU/DSU (DTE loop). If the problem
2.
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.
Swap out bad hardware, as required (CSU,
3.
DSU, switch, local or remote router).
Check the router configuration for the
1.
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.
If there are duplicate addresses, resolve the
4.
conflict by changing one of the IP addresses.
20-7