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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

TCP/IP Communication Verification Utility (ping/ping6) 1 2 3 4 TCP/IP Address Resolution Protocol Utility (arp)

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.

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.

TCP/IP Communication Verification Utility (ping/ping6) 1 2 3 4 TCP/IP Address Resolution Protocol Utility (arp)