[39628] in North American Network Operators' Group
Re: PPPOE, MTU, and boom.
daemon@ATHENA.MIT.EDU (Alex Rubenstein)
Thu Jul 19 01:07:07 2001
Date: Thu, 19 Jul 2001 01:11:41 -0400 (Eastern Daylight Time)
From: Alex Rubenstein <alex@nac.net>
To: Scott Silzer <scotts@iprimus.ca>
Cc: "nanog@nanog.org" <nanog@nanog.org>
In-Reply-To: <p05100309b77af10d71bb@[192.168.1.69]>
Message-ID: <Pine.WNT.4.33.0107181504390.1628-100000@phosphorus.nac.net>
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Errors-To: owner-nanog-outgoing@merit.edu
> This section describes possibly unexpected behavior that are resolved
> in Release 12.2(2)XH.
>
> CSCds69577
>
> Starting with Release 12.2(2)XH, you can resolve this problem by
> changing the value of the maximum segment size (MSS) contained
> in the MTU to 1492 or less. Use the following IOS command:
>
> ip tcp adjust-mss mss
>
> where mss is 1492 or less.
Post-mortem: this seems to work. Hoever, mss is 1460 or less, assuming mtu
is 1492.
dsl1.ahr(config-if)#ip tcp adjust-mss ?
<500-1460> Maximum segment size in bytes
Key (which took me a moment to figure out): the mss MUST be AT LEAST 32
bytes or more less than MTU; for a while, I had MTU set to 1400 on the
aggregation side, and didn't realise it, and this didn't work. As soon as
I upped the MTU to 1492, all started working, including all broken sites
and quicken.
