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TCP/IP Route Tracing Utility (traceroute/tracert/traceroute6)
(Page 3 of 4)
Basic Use of the traceroute Utility
Table 287
shows an example of a traceroute sent between two of the UNIX
computers I use on a regular basis. I added the “-q2” parameter
to change the default of three dummy messages per hop to two, so the
output would fit better in its display table. In this case, the servers
are separated by 14 hops. Notice how the elapsed time generally increases
as the distance from the transmitting device increases, but it is not
consistent because of random elements in the delay between any two devices
(see the incongruously-large value in hop #10, for example). Also notice
the asterisk (“*”) in the seventh hop, which means that no
response was received before the timeout period for the second transmission
with a TTL value of 7. Finally, there is no report at all for
hop #13; this machine may have been configured not to send Time Exceeded
messages.
Table 287: Route Tracing Using the traceroute Utility
traceroute
-q2 www.pcguide.com
traceroute to www.pcguide.com (209.68.14.80), 40 hops max, 40
byte packets
1 cisco0fe0-0-1.bf.sover.net (209.198.87.10) 1.223 ms 1.143 ms
2 cisco1fe0.bf.sover.net (209.198.87.12) 1.265 ms 1.117 ms
3 cisco0a5-0-102.wnskvtao.sover.net (216.114.153.170) 8.004 ms 7.270
ms
4 207.136.212.234 (207.136.212.234) 7.163 ms 7.601 ms
5 sl-gw18-nyc-2-0.sprintlink.net (144.232.228.145) 15.948 ms 20.931
ms
6 sl-bb21-nyc-12-1.sprintlink.net (144.232.13.162) 21.578 ms 16.324
ms
7 sl-bb27-pen-12-0.sprintlink.net (144.232.20.97) 18.296 ms *
8 sl-bb24-pen-15-0.sprintlink.net (144.232.16.81) 18.041 ms 18.338
ms
9 sl-bb26-rly-0-0.sprintlink.net (144.232.20.111) 20.259 ms 21.648
ms
10 sl-bb20-rly-12-0.sprintlink.net (144.232.7.249) 132.302 ms 37.825
ms
11 sl-gw9-rly-8-0.sprintlink.net (144.232.14.22) 23.085 ms 20.082
ms
12 sl-exped4-1-0.sprintlink.net (144.232.248.126) 43.374 ms 42.274
ms
13 * *
14 pcguide.com (209.68.14.80) 41.310 ms 49.455 ms
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Additional “unusual”
results may be displayed under certain circumstances. For example, the
traceroute program may display a code such a “!H”, “!N”
or “!P” to indicate receipt of an unexpected Destination
Unreachable message for a host, network, or protocol, respectively.
Other error messages may also exist, depending on the implementation.
 Note: Not all traceroute utility implementations use the technique described above. Microsoft’s tracert works not by sending UDP packets but rather ICMP Echo messages with increasing TTL values. It knows it has reached the final host when it gets back an Echo Reply message. A special ICMP Traceroute message was also developed in 1993, which was intended to improve the efficiency of traceroute by eliminating the need to send many UDP messages for each route tracing. Despite its technical advantages, since it was introduced long after TCP/IP was widely deployed, it never became a formal Internet standard and is not seen as often as the traditional method.
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