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Suppose that we do a traceroute www.google.com, then the parameter "max hops" will be set to 30 by default since we didn't specify it.

Now lets say that somehow the traceroute reaches the 30th hop before finding www.google.com, what would be the response given by the 30th router? is it a "port unreachable" response (like the destiny host would answer if we had reached him) or is it an ICMP response indicating that max hops was reached?

Santiago Hitta
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2 Answers2

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The response will be an ICMP response with TTL time expired like the previous hops. The difference between hops is only the TTL field. The routers on the path to www.google.com don't know you are trying to traceroute to google and infact don't know how many hops are between you and them. The way traceroute works is by sending packets with increasing TTL's until reaching the destination. Until reaching the destination most of the replies you will get are TTL time expired unless some other error has occured.

ashavitt
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currently the max hop can be set to 255

$ traceroute -m 255 www.google.com

if the destination is not reached before the max hop. it sends the acknowledgement
back to the source indicating packet is dead.

Abhishek D K
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