Re: path MTU bug still there?

From: Jonathan Morton (chromatix@cyberspace.org)
Date: Mon Jan 01 2001 - 09:59:12 EST


On Sun, 31 Dec 2000, Alan Cox wrote:

> > How is this solved? Personally, I am behind a CIPE tunnel with an MTU of
> > 1442 or something like that. I experienced problems to some places and
>
> You have to get the other end to fix it.
>
> > Could it be some kind of incompability at the tunnel level that make you
> > unable to receive large packets over the tunnel? Have you tcpdump:ed to
> > see if the tunnel packets actually make it the way they should?
>
> Its normally seriously incompetent firewall admins on remote sites. Most
>large
> ecommerce sites have these kind of basic errors. Makes you glad to trust your
> credit card details to them doesnt it 8)

In the past few days I encountered an MTU problem on the Internet - some
incompetent admin seemed to have set a low MTU on their router *and* prevented
"can't fragment" messages from being sent from it. The result was my SSH
tunnel
kept stalling when the route happened to use that particular router. I fixed
the problem by lowering the MTU on my dial-up PPP connection.

I have also had problems with stalling connections under other circumstances,
but I don't think the kernel or MTU are responsible - yet!

--------------------------------------------------------------
from: Jonathan "Chromatix" Morton
mail: chromi@cyberspace.org (not for attachments)
big-mail: chromatix@penguinpowered.com
uni-mail: j.d.morton@lancaster.ac.uk

The key to knowledge is not to rely on people to teach you it.

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