[33454] in North American Network Operators' Group
RE: IPIP-tunnel with 1500 MTU
daemon@ATHENA.MIT.EDU (Mikael Abrahamsson)
Thu Jan 11 14:57:26 2001
Date: Thu, 11 Jan 2001 20:37:15 +0100 (CET)
From: Mikael Abrahamsson <swmike@swm.pp.se>
To: "'nanog@merit.edu'" <nanog@merit.edu>
In-Reply-To: <FDEDA1BCEEBFD4118FFB00508BB1940B3EC35E@eahq-mb2.ea.com>
Message-ID: <Pine.LNX.4.30.0101112035190.20762-100000@uplift.swm.pp.se>
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Errors-To: owner-nanog-outgoing@merit.edu
On Thu, 11 Jan 2001, Bulger, Tim wrote:
> There is an 'ip mtu' option in the tunnel interface config on Cisco routers
> that you can set to 1500.. This will cause the tunnel packets themselves to
> be ip fragmented outbound on the router, hence shifting the fragmentation
> away from your internal network packets and over to the tunnel packets. I
> know that this works with GRE and IP/IP on Cisco routers running 12.x code.
(config-if)#tunnel mode gre ip
(config-if)#mtu 1500
% Interface Tunnel1 does not support adjustable maximum datagram size
I believe this is only true if you have serial links that support MTU >
1500 all the way between the two routers doing the tunneling, right?
--
Mikael Abrahamsson email: swmike@swm.pp.se
