[cisco-bba] MTU challenges on Cisco 7206VXR

[Frank Bulk]

Thanks for all the feedback on and offlist.  I put 
	mtu 1492
	ip tcp adjust-mss 1452
in production during a maintenance window this morning and things have been
working fine.

Regards,

Frank

-----Original Message-----
From: cisco-bba-bounces at puck.nether.net
[mailto:cisco-bba-bounces at puck.nether.net] On Behalf Of Jonty Bale
Sent: Tuesday, November 11, 2008 5:57 AM
To: cisco-bba at puck.nether.net
Subject: Re: [cisco-bba] MTU challenges on Cisco 7206VXR


> -----Original Message-----
> From: cisco-bba-bounces at puck.nether.net
> [mailto:cisco-bba-bounces at puck.nether.net] On Behalf Of Frank Bulk
> Sent: 06 November 2008 16:38
> To: cisco-bba at puck.nether.net
> Subject: Re: [cisco-bba] MTU challenges on Cisco 7206VXR
>
> Let me expand the question:
>
> What combination of:
>       mtu xxxx
>       ip tcp adjust-mss yyyy
>       ppp mtu adaptive
> should I be using on a Virtual Template?  I have none of them
> today, and
> only with PPPoE do things break sometimes.

ip tcp adjust-mss should be about 40 less than the max MTU you can
support (20 for the ip header, and 20 for the tcp).

We have to support a MTU of 1460 for some pppoa clients due to various
l2tp suppliers and access routers that don't support mtu > 1500.  We use
a number of virtual-templates depending on the l2tp supplier.

Can be a bit of a headache sometimes - great tool for clients to
diagnose issues is mturoute:

http://www.elifulkerson.com/projects/mturoute.php

Jonty.
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