interpretation of output from traceroute - TCP-IP

This is a discussion on interpretation of output from traceroute - TCP-IP ; Folk, A diagram of my network is visible. http://carnot.yi.org/Network.jpg I aim to have SMTP from Cantor, via the tunnel to Joule and thence to shawmail.gv.shawcable.net. On Joule, this seems reasonable. joule:~# traceroute -p 25 shawmail.gv.shawcable.net traceroute to shawmail.gv.shawcable.net (24.71.223.43), 30 ...

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Thread: interpretation of output from traceroute

  1. interpretation of output from traceroute

    Folk,

    A diagram of my network is visible.
    http://carnot.yi.org/Network.jpg

    I aim to have SMTP from Cantor, via the tunnel to Joule
    and thence to shawmail.gv.shawcable.net.

    On Joule, this seems reasonable.
    joule:~# traceroute -p 25 shawmail.gv.shawcable.net
    traceroute to shawmail.gv.shawcable.net (24.71.223.43), 30 hops max,
    40 byte packets
    1 24.108.32.1 (24.108.32.1) 11.480 ms 11.465 ms 11.500 ms
    2 rd1cv-ge3-3-4.gv.shawcable.net (64.59.166.162) 13.077 ms 13.116
    ms 13.079 ms
    3 rc2bb-pos0-1-5-0.vc.shawcable.net (66.163.77.185) 14.938 ms
    14.373 ms 14.390 ms
    4 rc2wh-tge0-15-1-0.vc.shawcable.net (66.163.69.121) 14.914 ms
    15.063 ms 15.031 ms
    5 rc1so-pos1-0-0.cg.shawcable.net (66.163.77.198) 28.026 ms 28.718
    ms 28.759 ms
    6 * * *
    ...
    30 * * *

    On Dalton, this puzzles me.
    dalton:~# traceroute -p 25 shawmail.gv.shawcable.net
    traceroute to shawmail.gv.shawcable.net (64.59.128.135), 30 hops max,
    40 byte pa
    ckets
    1 joule.petershouse.invalid (10.4.0.1) 17.036 ms 15.609 ms 16.434
    ms
    2 joule.petershouse.invalid (10.4.0.1) 16.445 ms 19.240 ms 19.277
    ms

    Q1. Why is 10.4.0.1 reported twice?

    Q2. Why does traceroute from Dalton stop at 10.4.0.1
    rather than continue to 24.108.32.1 and etc.

    I'm asking in this forum because I have no insight
    whether this problem is in routing, or in Exim
    configuration or in Shorewall configuration or in
    OpenVPN configuration or in the ISP. Any clues
    appreciated.

    Thanks, ... Peter E.

  2. Re: interpretation of output from traceroute

    On Nov 2, 6:08*am, peasth...@shaw.ca wrote:

    What's Dalton's default route? What source address is Dalton choosing
    for the traceroute?

    About 8 out of 10 times, when a traceroute appears to stop at node X,
    it's actually stopping one node further, as the next node has no idea
    how to get the reply packets *back*.

    Do a tcpdump on both Dalton and Joule and repeat the traceroute.

    DS

  3. Re: interpretation of output from traceroute

    David & others,

    On Sun, 2 Nov 2008 18:20:12 -0800 (PST) David Schwartz wrote,
    ds> What's Dalton's default route?

    dalton:/etc/openvpn# netstat -r
    Kernel IP routing table
    Destination Gateway Genmask Flags MSS Window
    irtt Iface
    shawmail.cg.sha joule.petershou 255.255.255.255 UGH 0 0
    0 tun0
    64.59.128.135 joule.petershou 255.255.255.255 UGH 0 0
    0 tun0
    joule.petershou * 255.255.255.255 UH 0 0
    0 tun0
    142.103.107.128 * 255.255.255.128 U 0 0
    0 eth0
    172.24.1.0 * 255.255.255.0 U 0 0
    0 eth3
    172.23.5.0 joule.petershou 255.255.255.0 UG 0 0
    0 tun0
    default 142.103.107.254 0.0.0.0 UG 0 0
    0 eth0

    The default route is conventional Internet;
    but the route to the shawmail addresses,
    24.71.223.43 and 64.59.128.135, is through
    the OpenVPN tunnel using tun0.

    ds> What source address is Dalton choosing for the traceroute?
    .... Do a tcpdump on both Dalton and Joule and repeat the traceroute.

    While tshark was running on Dalton I ran the traceroute.
    As Wireshark displays the tshark log, the content
    of a tunnel packet is not evident. I would need to
    decode the binary data to be convinced a packet
    contains traceroute data; this would be a challenge.
    The pattern of tunnel packets is consistent with the
    trace but I am not certain of the source address.

    I still need to install tshark on Joule; it might
    help.

    What else can be done?

    Thanks, ... Peter E.

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