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System Management Commands
traceroute
SPS208G/SPS224G4/SPS2024 Command Line Interface Reference Guide 439
31
Default Configuration
The default number of bytes in a packet is 40.
The default maximum TTL value is 0.
The default number of probes to be sent at each TTL level is 3.
The default timeout interval in seconds is 3.
Command Mode
User EXEC mode
User Guidelines
The traceroute command takes advantage of the error messages generated by
the devices when a datagram exceeds its time-to-live (TTL) value.
The traceroute command starts by sending probe datagrams with a TTL value of
one. This causes the first 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 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 by pressing Esc.
Example
The following example discovers the routes that packets will actually take when
traveling to their destination.
Console> traceroute umaxp1.physics.lsa.umich.edu