Specifications

Chapter 6 Configuring a Leased Line
Troubleshooting Problems with Leased Lines
6-8
Cisco 1700 Series Router Software Configuration Guide
78-5407-03
Table 6-1 Possible Causes of and Suggested Actions for Solving Problems with Leased Lines
Line State Possible Cause Suggested Actions
Serial0 is down,
line protocol is
down.
The router is not sensing a Carrier
Detect (CD) signal as a result of one
of the following:
• Telephone company problem,
such as the line is down or not
connected to the data service
unit / channel service unit
(DSU/CSU).
• Faulty or incorrect cabling of
the router.
• Local DSU/CSU hardware
failure.
• Local router hardware failure.
The following are some steps you can take
to isolate the problem:
• Check the LEDs on the external
DSU/CSU for CD activity.
• Refer to the Hardware Installation
Guide to confirm that your router is
correctly installed, using the
appropriate cables.
• Contact the telephone company to
determine if the leased line is down or
not connected.
• Connect the leased line to another port,
if possible. If the connection comes up,
there is a hardware failure on the Serial
0 port. Contact your Cisco reseller.
Serial0 is up,
line protocol is
down.
Possible causes for this line state are
• Local or remote router
misconfigured.
• The remote router is not
sending keepalive packets.
• Problem with the leased line.
• The serial clock transmit
external is not set on the
DSU/CSU.
• Local or remote DSU/CSU
hardware failure.
• Router hardware failure.
The following are some steps you can take
to isolate the problem:
• Perform DSU/CSU loopback tests.
During local loopback, enter the
show interface ser0 command. If the
line protocol is shown as up, there
might be a problem with the telephone
company, or the remote router might be
down.
• Refer to the Hardware Installation
Guide to confirm that your router is
correctly installed, using the
appropriate cables.
• Connect the leased line to another port,
if possible. If the connection comes up,
there is a hardware failure on the Serial
0 port. Contact your Cisco reseller.