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Configuring the Data Link Layer Protocol for E1, T1, and Serial Interfaces
Troubleshooting Logical Interfaces
The CLI displays events dealing with the establishment and negotiation of connec-
tion as they occur. You can then determine when and why problems occur.
LMI statistics report on the LMI messages that are exchanged between the
Frame Relay DTE and the DCE. The DCE uses LMI messages to advertise its
DLCI. In addition, the LMI messages serve as a local keepalive, indicating that
the interface is receiving polls from the other end of the connection.
Clear Counters. If you view the LMI statistics, you will see a running count
of polls sent and received, including those incremented before the interface
began having a problem. Because you are not interested in how many polls
the interface was receiving when it was functioning properly, you should reset
the counters to isolate the problem. To reset all counters associated with a
Frame Relay interface, enter the following command from the enable mode
context:
Syntax:
clear counters frame-relay <number>
After you clear the counters, you can reproduce the problem and then view
the LMI statistics to check whether the interface is receiving polls.
Troubleshooting HDLC
You should begin troubleshooting the HDLC interface by entering the show
interface hdlc command. From the enable mode context, enter:
Syntax: show interface hdlc <number>
Replace <number> with the number you assigned the HDLC interface.
If the HDLC interface is administratively down, enter no shutdown from the
HDLC interface configuration mode context. If the HDLC interface is down,
check the running-config to ensure that the HDLC interface is bound to the
correct physical interface. From the enable mode context, enter:
Syntax: show running-config interface hdlc <number>
Debug HDLC. You can view real-time events about the HDLC interface by
entering:
Syntax: debug hdlc [errors | verbose]
Use the errors option to view statistics and messages about protocol errors.
Use the verbose option to increase the level of detail provided in the debug
messages.
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