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    SubjectRe: path MTU bug still there?
    On Sun, 31 Dec 2000, Mikael Abrahamsson wrote:

    > When the linux box does TCP to the outside it'll use the MTU of
    > the tunnel (default route is the tunnel) and thus works perfectly
    > (since TCP MSS will be set low enough to fit into the tunnel).

    In my case I can't access a problematic host even from the router
    box.

    > Could it be some kind of incompability at the tunnel level that
    > make you unable to receive large packets over the tunnel?

    Could be. The internet connection is a 64k ISDN link.

    > Have you tcpdump:ed to see if the tunnel packets actually make it
    > the way they should?

    I can't snoop the actual tunnel device, because tcpdump and sniffit
    give me an unknown media type error. Here's a tcpdump from the router
    box's ethernet device of a HTTP session (using lynx) to
    www.doomworld.com:

    17:19:46.126297 xxx.xxx.xxx.xxx.1029 > 206.96.221.6.80: S 2549095564:2549095564(0) win 32120 <mss 1460,sackOK,timestamp 649398[|tcp]> (DF)
    17:19:46.386142 206.96.221.6.80 > xxx.xxx.xxx.xxx.1029: S 1631828281:1631828281(0) ack 2549095565 win 30660 <mss 1460,sackOK,timestamp 91687185[|tcp]> (DF)
    17:19:46.386142 206.96.221.6.80 > xxx.xxx.xxx.xxx.1029: S 1631828281:1631828281(0) ack 2549095565 win 30660 <mss 1460,sackOK,timestamp 91687185[|tcp]> (DF)
    17:19:46.386142 xxx.xxx.xxx.xxx.1029 > 206.96.221.6.80: . ack 1 win 32120 <nop,nop,timestamp 649423 91687185> (DF)
    17:19:46.386142 xxx.xxx.xxx.xxx.1029 > 206.96.221.6.80: P 1:369(368) ack 1 win 32120 <nop,nop,timestamp 649423 91687185> (DF)
    17:19:46.685963 206.96.221.6.80 > xxx.xxx.xxx.xxx.1029: . ack 369 win 30660 <nop,nop,timestamp 91687216 649423> (DF)
    17:19:46.685963 206.96.221.6.80 > xxx.xxx.xxx.xxx.1029: . ack 369 win 30660 <nop,nop,timestamp 91687216 649423> (DF)

    And the connection locks up. This happens every time. I don't have
    access to the Cisco so I can't dump traffic on the remote end of
    my tunnel.

    --
    -=[ Count Zero / TBH - Jussi Hämäläinen - email count@theblah.org ]=-

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