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Tracing route of ip address tracert etc.

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  • 03-06-2008 3:41am
    #1
    BrokenArrows
    Registered Users Posts: 7,498 ✭✭✭


    Hi just a quick question. Not sure it belongs in the programmming thread but here it goes.

    Why does running a tracert take so long to return the information for each stop along the way?


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    #2
    DublinDilbert
    Registered Users Posts: 5,379 ✭✭✭DublinDilbert


    BrokenArrows wrote: »
    Hi just a quick question. Not sure it belongs in the programmming thread but here it goes.

    Why does running a tracert take so long to return the information for each stop along the way?

    Well from memory its using error messages generated when the TTL field reaches zero. The error message usually contains the host name, which tracert will display to the user.

    So the first ICMP request tracert sends out with TTL = 1, the first router this hits decrements the TTL to 0 then sends back a message saying can't route this any further... the next ICMP request is sent out with TTL = 2, the second router will set the TTL = 0, and return an error message etc...


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    #3
    seamus
    Registered Users Posts: 68,317 ✭✭✭✭seamus


    I think actually what he's referring to is the reverse dnslookup that's done for each node along the way.

    It basically attempts to query by IP address to find the name of each host. Reverse lookups can be a bit slower than normal lookups, but in reality you tend to see a delay in cases where it's tougher to do a reverse lookup, such as for internal IP addresses, because the program may have to wait for the lookup to time out.

    In Windows, if you run tracert with the -d parameter, it won't do a lookup for each host and should run faster.


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