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Chapter 7
Troubleshooting Serial Line and Frame Relay Connectivity
Interface is in loopback
mode
1. Check the interface configuration.
2. If there is a loopback entry in the interface
configuration, remove it with the no form of
the command.
3. If the interface configuration is clean, check
the CSU/DSU to see if it is placed in loopback.
4. If it is, remove the CSU/DSU from loop-
back mode.
5. If the CSU/DSU is not in loopback mode,
contact the local provider; it may have placed
the circuit in loopback.
Interface is administratively
down
1. Check the configuration. Verify that the IP
address is not a duplicate.
2. Enter the configuration mode and issue the
no shutdown
command within the interface.
Line speed is larger than
the interface capacity
1. Reduce input queue size by using the
hold-queue in
command.
2. Increase output queues on exiting interfaces.
Interface speed is larger
than the line speed
1. Reduce broadcast traffic.
2. Increase output queue.
3. Implement queuing algorithms, if necessary.
T A B L E 7 . 2
Action Plans for Common Serial Line Problems (continued)
Problem
Resolution Action Plan
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