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What is traceroute?


If you can't solve your routing problems by looking at the routing tables and interfaces, a useful program for helping solve the problem is traceroute. Solaris 2.7 software bundles the popular traceroute utility. Unfortunately, this program is not shipped with SunOS or Solaris prior to 2.7, and as a result is not supported by SunService. However, you can easily find a copy on the internet. The ftp site contains traceroute under the /pub/tools directory. If you consult 'archie' or other searching programs, it is likely that you will be able to find a more local copy. Traceroute works by sending out a set of 3 UDP packets. These packets are initially given a Time-To-Live of 1 hop, which is then increased to 2 hops, then to 3, etc.... until the packets reach the remote machine. This has the effect of stepping through the routers leading towards a destination machine, one at a time. However, it also causes you to only see a unidirectional route, from your client to the destination machines. It's quite possible for routes to be different going from and to a machine, and traceroute will not standardly show this. For example, if packets followed the following path: --> C --> A B <-- D <-- A traceroute from A to B would show: A, C, B, while a traceroute from B to A would show: B, D, A.

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