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When tracerouting a destination and going through all these hops, what happens during this process? Does ICMP have an initial counter and decrements this counter on each hop it passes? If the counter is initiated to be 30, how will this work on a RIP network? RIP has knowledge only about 15 hops and that's where it quits.

Thanks for your answers!

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"Traceroute works by sending packets with gradually increasing TTL value, starting with TTL value = 1. The first router receives the packet, decrements the TTL value and drops the packet because it then has TTL value zero. The router sends an ICMP Time Exceeded message back to the source. The next set of packets are given a TTL value of 2, so the first router forwards the packets, but the second router drops them and replies with ICMP Time Exceeded. Proceeding in this way, traceroute uses the returned ICMP Time Exceeded messages to build a list of routers that packets traverse, until the destination is reached and returns an ICMP Echo Reply message."

Source.

http://en.wikipedia.org/wiki/Traceroute

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I would add that it explains why sone odes aren't responding. they allow ICMP echo packets forwarding but won't answer to them even if they drop it. –  Kwaio Aug 28 '13 at 12:48

You can define the maximum number of hops in an ICMP package. For each hop this counter is decremented and when 0 is reached an error is sent back.

Traceroute begins with a maximum number of 1 hop and increments after each error the value by one and determines by the collected error returns the route to the destination.

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you did not explain it how this would work in a network that uses RIP routing protocol –  holasz Aug 28 '13 at 12:22

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