MTU handling in 6RD deployments

Mikael Abrahamsson swmike at
Tue Jan 7 13:30:49 CET 2014

On Tue, 7 Jan 2014, Mark Townsley wrote:

> Note I've heard some ISPs consider running Jumbo Frames under the covers 
> so that IPv4 could carry 1520 and 1500 would be possible for IPv6, but 
> have not yet seen that confirmed to me in practice.

Unless this is done in a very controlled environment I'd say this is 
bordering on the impossible. There are so many failure points for a jumbo 
solution it's scary. Most of them is also silent failure of PMTUD, 
basically blackholing of traffic.

Yes, it can be done of course, but I'd say operationally it's easier to 
just drop the MTU to 1480 and known working, than the jumbo alternative.

Mikael Abrahamsson    email: swmike at

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