Understanding Pathping / Tracert - TCP-IP

This is a discussion on Understanding Pathping / Tracert - TCP-IP ; Note I am behind a router (192.168.0.1). Am I correct to assume that this Dlink router is not allowing itself to be pinged and therefore shows as "timed out" on any tracert to any external site (all my tracerts look ...

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Thread: Understanding Pathping / Tracert

  1. Understanding Pathping / Tracert

    Note I am behind a router (192.168.0.1). Am I correct to assume that
    this Dlink router is not allowing itself to be pinged and therefore
    shows as "timed out" on any tracert to any external site (all my
    tracerts look the same, 2nd hop tiems out always)? Can anyone explain
    the 1st and 2nd hops in the tracert below? I assume the 1st is the
    internal side of my router, and the 2nd is the external side of my
    router. Am I correct?

    Tracing route to www.l.google.com [72.14.205.147] over a maximum of 30
    hops:

    1 <1 ms <1 ms <1 ms 192.168.0.1
    2 * * * Request timed out.
    3 * * 8 ms 66.185.90.1
    4 8 ms 8 ms 10 ms 24.153.5.45
    5 9 ms 8 ms 7 ms 24.153.7.181
    6 9 ms 9 ms 8 ms 64.71.240.29

    Trace complete.


    Also... here's a pathping of www.google.com ... Why doesnt it show me
    any details, it makes it look like theres only 2 hops... why? I
    assume its related to my question above?


    Tracing route to www.l.google.com [72.14.205.147] over a maximum of 30
    hops:

    0 192.168.0.202
    1 192.168.0.1
    2 * * *

    Computing statistics for 50 seconds...

    Source to Here This Node/Link
    Hop RTT Lost/Sent = Pct Lost/Sent = Pct Address

    0
    192.168.0.202
    0/ 100 =
    0% |
    1 0ms 0/ 100 = 0% 0/ 100 = 0% 192.168.0.1
    100/ 100 =100% |
    2 --- 100/ 100 =100% 0/ 100 = 0% 0.0.0.0

    Trace complete.


  2. Re: Understanding Pathping / Tracert

    In article <1180768539.428399.83790@m36g2000hse.googlegroups.c om>,
    Dennis wrote:
    >Note I am behind a router (192.168.0.1). Am I correct to assume that
    >this Dlink router is not allowing itself to be pinged and therefore
    >shows as "timed out" on any tracert to any external site (all my
    >tracerts look the same, 2nd hop tiems out always)?


    >Tracing route to www.l.google.com [72.14.205.147] over a maximum of 30
    >hops:


    > 1 <1 ms <1 ms <1 ms 192.168.0.1
    > 2 * * * Request timed out.
    > 3 * * 8 ms 66.185.90.1


    No, your router, 192.168.0.1, *is* responding, so it cannot be
    the case that 'this Dlink router is not allowing itself to be pinged
    and therefore shows as "timed out"'.

    However, it could easily be the case that the next hop out from
    you, the first ISP hop, is refusing to send back packets that
    would be recognized by your tracert .

    Note that tracert does not ping each path point individually,
    because it doesn't know what those path points are ahead of time.
    Instead what it does is attempt to ping the final destination,
    setting the Time To Live (TTL) field incrementally higher, and
    hoping that intermediate hops along the way will respond with
    ICMP Time Exceeded messages when they see that the TTL field
    has decremented to 0. Thus even if it were the Dlink that was not
    responding (rather than the hop after that), it is not correct
    to think of whichever device as "not allowing itself to be pinged",
    because the tracert ping is not directed to that device: the device
    that is not showing up, is not showing up because it is not
    returning ICMP Time Exceeded messages -- which have only to do with
    the IP-level TTL counter and do not have to do with ping specifically.

    The mechanisms are slightly different for Unix traceroute (which uses
    UDP packets instead of ICMP Echo packages), but the reliance on
    ICMP Time Exceeded messages is exactly the same.

  3. Re: Understanding Pathping / Tracert

    On Jun 2, 11:10 am, rober...@hushmail.com (Walter Roberson) wrote:
    > However, it could easily be the case that the next hop out from
    > you, the first ISP hop, is refusing to send back packets that
    > would be recognized by your tracert .



    Great info, thanks Walter. I follow you mostly, but I'm still a bit
    confused about why pathping stops on the 2nd hop. Mind if I pick your
    brain a bit more?

    Am I correct to say: TRACERT focuses on the destination, and records
    the responses it gets from each hop "after the fact". Whereas PATHPING
    is working on each hop individually and that is why it fails on the
    2nd hop and goes no further? Does this 2nd hop (my ISP) completely
    make pathping useless on my system? ie: How could I test the
    packetloss of a router 5 hops away from me if my ISP is crushing my
    pathping on the 2nd hop?


    Thanks again




  4. Re: Understanding Pathping / Tracert

    In article <1180806883.850857.203460@q69g2000hsb.googlegroups. com>,
    Dennis wrote:

    > On Jun 2, 11:10 am, rober...@hushmail.com (Walter Roberson) wrote:
    > > However, it could easily be the case that the next hop out from
    > > you, the first ISP hop, is refusing to send back packets that
    > > would be recognized by your tracert .

    >
    >
    > Great info, thanks Walter. I follow you mostly, but I'm still a bit
    > confused about why pathping stops on the 2nd hop. Mind if I pick your
    > brain a bit more?
    >
    > Am I correct to say: TRACERT focuses on the destination, and records
    > the responses it gets from each hop "after the fact". Whereas PATHPING
    > is working on each hop individually and that is why it fails on the
    > 2nd hop and goes no further? Does this 2nd hop (my ISP) completely
    > make pathping useless on my system? ie: How could I test the
    > packetloss of a router 5 hops away from me if my ISP is crushing my
    > pathping on the 2nd hop?


    Just ignore the 2nd hop, and look at what happens with the 5th hop.

    --
    Barry Margolin, barmar@alum.mit.edu
    Arlington, MA
    *** PLEASE post questions in newsgroups, not directly to me ***
    *** PLEASE don't copy me on replies, I'll read them in the group ***

  5. Re: Understanding Pathping / Tracert

    On Jun 2, 6:13 pm, Barry Margolin wrote:
    > In article <1180806883.850857.203...@q69g2000hsb.googlegroups. com>,
    >
    > Just ignore the 2nd hop, and look at what happens with the 5th hop.


    In this situation (see first post) pathping only shows two hops, then
    stops, it doesnt get to the 5th hop.

    Somehow the 2nd hop "ends" the pathping, and I'm trying to understand
    why.

    ?




  6. Re: Understanding Pathping / Tracert

    In article <1180897574.979742.131600@m36g2000hse.googlegroups. com>,
    Dennis wrote:

    > On Jun 2, 6:13 pm, Barry Margolin wrote:
    > > In article <1180806883.850857.203...@q69g2000hsb.googlegroups. com>,
    > >
    > > Just ignore the 2nd hop, and look at what happens with the 5th hop.

    >
    > In this situation (see first post) pathping only shows two hops, then
    > stops, it doesnt get to the 5th hop.
    >
    > Somehow the 2nd hop "ends" the pathping, and I'm trying to understand
    > why.
    >
    > ?


    I've never used pathping, but my guess is that it finds the routers to
    ping by doing a tracert, and the timeout from the 2nd hop is confusing
    it and preventing it from going any further. So maybe you need to find
    a better tool.

    --
    Barry Margolin, barmar@alum.mit.edu
    Arlington, MA
    *** PLEASE post questions in newsgroups, not directly to me ***
    *** PLEASE don't copy me on replies, I'll read them in the group ***

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