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Traceroute

What is #Traceroute & How it Works?

#TRACEROUTE
o  Traceroute is a network diagnostic tool, that is used to identify the number of hops in between Source and destination, and is also used to find the average time taken by an IP packet for each hop.
o  Source Device sends a packet starting with TTL 1 and once TTL expires on every device it increases the TTL until it gets a reply from the destination.
o  Every router in between Source and destination use an ICMP packet to reply
o  It uses destination port no from 33434 to 33464 (basically these ports are unused)
o  it will work only for 30 hops (give info only for 30 devices away from the source)
o  Every single packet uses a different UDP port no from 33434 to 33464.
o  it sends 3 packets for each hop by default (Traceroute program sends three packets to each hop to measure the exact average round trip time)
o the First packet will go with TTL 1 and when the next-hop receives that packet it will decrement the TTL value by 1 and if it gets zero then it will send TTL that exceeds msg to pc And Source will get to know the first router in that way.
o  Then again Source will send a packet with TTL 2 and when 2nd router in that way gets that packet then it will send  TTL exceeds msg to Source Device and again Source Device will get to know another router in that way and process will continue until packet goes to correct destination.
o  when the packet reaches its exact destination it will send a port unreachable msg to Source Device, and the traceroute process will complete.

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