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Table Of Contents  The TCP/IP Guide
 9  TCP/IP Application Layer Protocols, Services and Applications (OSI Layers 5, 6 and 7)
      9  TCP/IP Key Applications and Application Protocols
           9  TCP/IP Administration and Troubleshooting Utilities and Protocols

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TCP/IP Communication Verification Utility (ping/ping6)
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TCP/IP Address Resolution Protocol Utility (arp)
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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


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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TCP/IP Communication Verification Utility (ping/ping6)
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TCP/IP Address Resolution Protocol Utility (arp)
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