Information Technology Reference
In-Depth Information
15
CHAPTER
Troubleshooting Serial Lines
This chapter presents general troubleshooting information and a discussion of tools and techniques for
troubleshooting serial connections. The chapter consists of the following sections:
Troubleshooting Using the
show interfaces serial
Command
•
Using the
show controllers
Command
•
Using
debug
Commands
•
Using Extended
ping
Tests
•
Troubleshooting Clocking Problems
•
Adjusting Buffers
•
Special Serial Line Tests
•
Detailed Information on the
show interfaces serial
Command
•
Troubleshooting T1 Problems
•
Troubleshooting E1 Problems
•
Troubleshooting Using the show interfaces serial Command
The output of the
show interfaces serial
exec command displays information specific to serial
interfaces. Figure 15-1 shows the output of the
show interfaces serial
exec command for a High-Level
Data Link Control (HDLC) serial interface.
This section describes how to use the
show interfaces serial
command to diagnose serial line
connectivity problems in a wide-area network (WAN) environment. The following sections describe
some of the important fields of the command output.
Other fields shown in the display are described in detail in the section “Detailed Information on the
show
interfaces serial
Command,” later in this chapter.
Serial Lines: show interfaces serial Status Line Conditions
You can identify five possible problem states in the interface status line of the
show interfaces serial
display (see Figure 15-1):
Serial
x
is down, line protocol is down
•
Serial
x
is up, line protocol is down
•
