Using The Traceroute Command; Examples; Using Debug Commands - Cisco ASR 9000 Getting Started Manual

Chapter 6 Troubleshooting the Cisco IOS XR Software

Using the traceroute Command

Use the traceroute command in EXEC mode to discover the routes that packets take when traveling to
their destination. Enter a hostname or an IP address as an argument to this command.
This command works by taking advantage of the error messages generated by routers when a datagram
exceeds its time-to-live (TTL) value.
The traceroute command starts by sending probe datagrams with a TTL value of 1, causing the first
router to discard the probe datagram and send back an error message. The traceroute command sends
several probes at each TTL level and displays the round-trip time for each.
The traceroute command sends one probe at a time. Each outgoing packet may result in one or two error
messages. A time exceeded error message indicates that an intermediate router has seen and discarded
the probe. A destination unreachable error message indicates that the destination node has received the
probe and discarded it because it could not deliver the packet. If the timer times out before a response
comes in, the traceroute command prints an asterisk (*).
The traceroute command terminates when the destination responds, the maximum TTL is exceeded, or
the user interrupts the trace with the escape sequence.

Examples

In the following example, the route for an IP address appears:
RP/0/RSP0/CPU0:router# traceroute 10.233.233.233
Type escape sequence to abort.
Tracing the route to 10.233.233.233
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2

Using debug Commands

Debug commands are used to diagnose and resolve network problems. Use debug commands to
troubleshoot specific problems or during troubleshooting sessions.
Use debug commands to turn on or off debugging for a specific service or subsystem. When debugging
is turned on for a service, a debug message is generated each time the debugging code section is entered.
The following sections provide information on debugging:
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•
•
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Debug commands can generate a very large amount of output and can render the system unusable. Use
Caution
debug to troubleshoot specific problems or during specific troubleshooting sessions on systems that are
not in production.
OL-17502-01
F I N A L D R A F T — C i s c o C o n f i d e n t i a l
172.25.0.2 11 msec 2 msec
192.255.254.254 1 msec
Viewing a List of Debug Features, page 6-4
Enabling Debugging for a Feature, page 6-4
Viewing Debugging Status, page 6-5
Disabling Debugging for All Services Started at the Active Terminal Session, page 6-5
Disabling Debugging for All Services Started at All Terminal Sessions, page 6-6
1 msec
* 2 msec
Cisco ASR 9000 Series Aggregation Services Router Getting Started Guide
Basic Troubleshooting Commands
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