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Troubleshooting Serial Lines
393
Serial0: HDLC myseq 172189, mineseen 172189*, yourseen
172327, line up
Serial0: HDLC myseq 172190, mineseen 172190*, yourseen
172328, line up
Serial0: HDLC myseq 172191, mineseen 172191*, yourseen
172329, line up
Router_A#
The field values are very similar to the field values in the Frame Relay out-
put. Here are the field definitions:
mysec This is the local keepalive number. The value is the sequence identifier.
yourseen This is the keepalive sent by the other side of the serial connection.
mineseen This is the value of the keepalive sent by the local interface
seen by the remote side.
debug serial packet Command
The debug serial packet command is used to provide additional infor-
mation regarding serial interfaces. According to information contained in
CCO UniverCD, the debug serial packet only provides information
for interfaces that use SMDS encapsulation.
A sample output is not shown here because the information included in
the output is useful only when you have an understanding of the SMDS
protocol, which has not been discussed in this book.
CSU/DSU Loopback Tests
Loopback tests aid in physically isolating serial line and Frame Relay prob-
lems. Four different loopback tests can be performed to troubleshoot the
circuit. You can perform two of them, and the local provider has access to
perform the other two. Here is a list of four loopback tests:
Local loopback on the local CSU/DSU
Local loopback on the remote CSU/DSU
Remote loopback from the local NIU to the remote CSU/DSU
Remote loopback from the remote NIU to the local CSU/DSU
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