To discover the
routes that packets actually take when traveling to their destination across an
IP network, use the
traceroute
command in
XR EXEC mode.
traceroute [ipv4 | ipv6] [host-name | ip-address] [ {source | ip-address-name | interface-name}] [numeric] [timeout seconds] [probe count] [minttl seconds] [maxttl seconds] [port number] [priority number] [verbose]
Syntax Description
|
ipv4
|
(Optional) Specifies IPv4 address prefixes.
|
|
ipv6
|
(Optional) Specifies IPv6 address prefixes.
|
|
host-name
|
(Optional) Hostname of system to use as the destination of the trace attempt.
|
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ip-address
|
(Optional) Address of system to use as the destination of the trace attempt.
|
|
source
|
(Optional) Source address.
|
|
ip-address-name
|
(Optional) IP address A.B.C.D or hostname.
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numeric
|
(Optional) Numeric display only.
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timeout
seconds
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(Optional) Timeout value. Range is 0 to 3600.
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probe
count
|
(Optional) Probe count. Range is 0 to 65535.
|
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minttl
seconds
|
(Optional) Minimum time to live. Range is 0 to 255.
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|
maxttl
seconds
|
(Optional) Maximum time to live. Range is 0 to 255.
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|
port
number
|
(Optional) Port number. Range is 0 to 65535.
|
|
priority
number
|
(Optional) Packet priority. Range is 0 to 15. Available when the
ipv6
keyword is specified.
|
|
verbose
|
(Optional) Verbose output.
|
Command Default
No default
behavior or values
Command Modes
XR EXEC mode
Command History
|
Release
|
Modification
|
|
Release 6.0
|
This
command was introduced.
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Usage Guidelines
The default value
for the
traceroute
command refers only to the destination. No default value is available for the
destination address.
The
traceroute
command works by taking advantage of the error messages
generated by networking devices when a datagram exceeds its time-to-live (TTL)
value.
The
traceroute
command starts by sending probe datagrams with a TTL
value of 1, which causes the first networking device 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 out 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 networking device 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 goes off before a response comes in, the traceroute command prints an asterisk (*).
The
traceroute
command terminates when the destination responds, when the maximum TTL is
exceeded, or when the user interrupts the trace with the escape sequence, which
is, by default, Ctrl-C. Simultaneously press and release the Ctrl and C keys.
To use nondefault
parameters and invoke an extended
traceroute
test, enter the command without a
host-name or
ip-
address
argument. You are stepped through a dialog to select the desired parameter
values for the
traceroute
test.
Because of how IP
is implemented on various networking devices, the IP
traceroute
command may behave in unexpected ways.
Not all
destinations respond correctly to a probe message by sending back an “ICMP port
unreachable” message. A long sequence of TTL levels with only asterisks,
terminating only when the maximum TTL has been reached, may indicate this
problem.
There is a known
problem with the way some hosts handle an “ICMP TTL exceeded” message. Some
hosts generate an “ICMP” message, but they reuse the TTL of the incoming
packet. Because this value is zero, the ICMP packets do not succeed in
returning. When you trace the path to such a host, you may see a set of TTL
values with asterisks (*). Eventually the TTL is raised high enough that the
“ICMP” message can get back. For example, if the host is six hops away,
the
traceroute
command
times out on responses 6 through 11.
Task ID
|
Task ID
|
Operations
|
|
basic-services
|
read,
write, execute
|
Examples
The following
output shows a sample
traceroute
session when a destination hostname has been specified:
RP/0/RP0/CPU0:router# traceroute host8-sun
Type escape sequence to abort.
Tracing the route to 192.168.0.73
1 192.168.1.6 (192.168.1.6) 10 msec 0 msec 10 msec
2 gateway01-gw.gateway.cisco.com (192.168.16.2) 0 msec 10 msec 0 msec
3 host8-sun.cisco.com (192.168.0.73) 10 msec * 0 msec
The following
display shows a sample extended
traceroute
session when a destination hostname is not specified:
traceroute # traceroute
Protocol [ipv4]:
Target IP address: ena-view3
Source address: 10.0.58.29
Numeric display? [no]:
Timeout in seconds [3]:
Probe count [3]:
Minimum Time to Live [1]:
Maximum Time to Live [30]:
Port Number [33434]:
Loose, Strict, Record, Timestamp, Verbose[none]:
Type escape sequence to abort.
Tracing the route to 171.71.164.199
1 sjc-jpxlnock-vpn.cisco.com (10.25.0.1) 30 msec 4 msec 4 msec
2 15lab-vlan725-gx1.cisco.com (173.19.72.2) 7 msec 5 msec 5 msec
3 stc15-00lab-gw1.cisco.com (173.24.114.33) 5 msec 6 msec 6 msec
4 stc5-lab4-gw1.cisco.com (173.24.114.89) 5 msec 5 msec 5 msec
5 stc5-sbb4-gw1.cisco.com (172.71.241.162) 5 msec 6 msec 6 msec
6 stc5-dc5-gw1.cisco.com (172.71.241.10) 6 msec 6 msec 5 msec
7 stc5-dc1-gw1.cisco.com (172.71.243.2) 7 msec 8 msec 8 msec
8 ena-view3.cisco.com (172.71.164.199) 6 msec * 8 msec
This table
describes the characters that can appear in traceroute output.
Table 6. traceroute
Text Characters
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Character
|
Description
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xx msec
|
For each
node, the round-trip time in milliseconds for the specified number of probes.
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| *
|
Probe time
out.
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| ?
|
Unknown
packet type.
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A
|
Administratively unreachable. This output usually indicates that
an access list is blocking traffic.
|
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H
|
Host
unreachable.
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N
|
Network
unreachable.
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P
|
Protocol
unreachable.
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Q
|
Source
quench.
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U
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Port
unreachable.
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