MSN blocking PMTUD

Mikael Abrahamsson swmike at
Mon May 17 16:21:49 UTC 2004

On Mon, 17 May 2004, Miguel Mata-Cardona wrote:

> Is there somebody from MSN here? Is there a workaround for this 
> problem without using other type of tunneling? If not, is there any 
> other workaround?

Use "ip mtu 1500" on each tunnel interface. Uses more CPU but works.

"ip adjust-mss 1300" is also nice, in conjunction with the above you end 
up with the TCP traffic not being fragmented and it still being 
transparent for fullsize UDP traffic.

Mikael Abrahamsson    email: swmike at

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