Internet Exchanges supporting jumbo frames?

Mikael Abrahamsson swmike at
Wed Mar 9 15:58:51 UTC 2016

On Wed, 9 Mar 2016, Nick Hilliard wrote:

> used.  Some will want 9000, some 9200, others 4470 and some people

I have a strong opinion for jumboframes=9180bytes (IPv4/IPv6 MTU), partly 
because there are two standards referencing this size (RFC 1209 and 1626), 
and also because all major core router vendors support this size now that 
Juniper has decided (after some pushing) to start supporting it in more 
recent software on all their major platforms (before that they had too low 
L2 MTU to be able to support 9180 L3 MTU).

In order to deploy this to end systems, I however thing we're going to 
need something like to make this 
work on mixed-MTU LANs. The whole thing about PMTUD blackhole detection is 
also going to be needed, so hosts try lower PMTU in case larger packets 
are dropped because of L2 misconfiguration in networks.

With IPv6 we have the chance to make PMTUD work properly and also have 
PMTU blackhole detection implemented in all hosts. IPv4 is lost cause in 
my opinion (although it's strange how many hosts that seem to get away 
with 1492 (or is it 1496) MTU because they're using PPPoE).

Mikael Abrahamsson    email: swmike at

More information about the NANOG mailing list