Traceroute overview

Traceroute is a system administrators utility to trace the route IP packets take from a source system to some destination system.

Traceroute uses the IP TTL (Time To Live) parameter to find the route. It sends a packet with a TTL value equal to 1. The first router receives the packet and decreases the TTL. With a TTL equal to 0, the router sends a timeout back to traceroute, with this packet, traceroute knows about the first router. Now, traceroute sends another packet with a TTL equal to 2. The first router decreases the TTL and sends the packet to the second router which decreases it in turn: the TTL is equal to 0


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