[c-nsp] L2TPv3 with MTU difference

Rens rens at autempspourmoi.be
Mon May 4 03:18:34 EDT 2009

Nobody that can help me with this?

-----Original Message-----
From: cisco-nsp-bounces at puck.nether.net
[mailto:cisco-nsp-bounces at puck.nether.net] On Behalf Of Rens
Sent: vendredi 17 avril 2009 14:43
To: cisco-nsp at puck.nether.net
Subject: [c-nsp] L2TPv3 with MTU difference



I have an OSPF broadcast configured with several routers.


Some of the routers have a higher MTU then others so I use ip ospf mtu
ignore on all the neighbours. (to compensate with the fragmentation at
higher bandwidths)


I have routers with mtu 1600 and others have the default 1500 because of
FastEthernet interfaces


I have a L2TPv3 tunnel that runs over this IP network, when I configure a
tunnel between a router that has 1600 & 1500 mtu I can't pass any frames of


When doing 1518, the tester that is connected to the router that does 1600
is receiving them, but the tester that is connected to the router that does
1500 isn't receiving anything.


When I lower it to 1280 it works again.


All help welcome







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