strange thing in traceroute, last hop is my own ip-address

Discussion in 'Cisco' started by frank malone, Apr 8, 2006.

  1. frank malone

    frank malone Guest

    Hi!

    I found a strange thing with a traceroute.
    When I do a traceroute from a Cisco router to a Nortel-device (I do not know
    which exactly)
    the last hop (which is the Nortel-device) does not show its ip-address,
    instead it show the source-address
    of the device I was tracing from. If I try it with different
    source-addresses, I always see my own source-address
    as the last hop. This only happens with this one special device. If I do a
    traceroute to another device in the same net,
    I see the device's ip-address as the last hop.
    Does Nortel use a "trick" to manipulate the ip-address in the traceroute?
    Is it a simple security feature (you do not see me in the traceroute).

    Thanks.
    Frank
    frank malone, Apr 8, 2006
    #1
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  2. frank malone

    Guest

    It is possible that the Nortel device is manipulating the source IP
    address of the ICMP time-exceeded message that it sends back. If you
    don't expect lots of ICMP traffic to the box, you should be able to
    turn on "debug ip icmp" on the Cisco box safely and look at the output
    to see what the Nortel box is sending back to you in response to the
    traceroute probe and figure out if they are indeed using a bogus source
    IP address.

    Cisco da Gama
    http://ciscostudy.blogspot.com
    , Apr 8, 2006
    #2
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