Re: PMTU and Broken Servers

[Richard A Steenbergen <ras () e-gerbil net>]

On Thu, May 08, 2003 at 07:04:18PM +0200, Mikael Abrahamsson wrote:
> On Thu, 8 May 2003, Leo Bicknell wrote:
>
> > Could you define newer?  My limited testing with 12.0S and 12.2something
> > shows both returing MTU can't be set on a tunnel interface.
>
> You cannot change the MTU of the tunnel, but you can change the "ip mtu" 
> of the tunnel. I've done this on 7200 and 1600 that are running IOSes that 
> are at least a year old. The feature is at least 2-3 years old, because 
> that's the first time I encountered it.
>
> The router will do re-assembly on the tunnel level to be able to transfer 
> a 1500 byte sized IP packet non-fragmented.

Be warned, while fragmentation follows some form of fast path, reassembly
is process switched. A beefy 7206 will fragment 300Mbps easily, but will
reassemble around 30Mbps.

-- 
Richard A Steenbergen <ras () e-gerbil net>       http://www.e-gerbil.net/ras
GPG Key ID: 0xF8B12CBC (7535 7F59 8204 ED1F CC1C 53AF 4C41 5ECA F8B1 2CBC)