[AusNOG] [nznog] FW: Final phase of four-byte AS number policy begins 1 January 2010

Andy Davidson andy at nosignal.org
Fri Dec 18 20:18:13 EST 2009

Skeeve Stevens wrote:
> Hmmmm.. is this a good thing?
> I realise that few people go back for more ASN's after their initial one, but we are requesting them regularly for customers.
> What is the situation with carriers accepting them.  Could a few transit providers on these lists comment on whether they are ready to handle 4byte AS Numbers in their BGP products.

There is a 'compatibility mode' - someone who does not understand the
4-byte world can build a session facing AS23456, and the adjacency will work.

Of course, the carrier will end up with a lot of sessions facing 23456
which shall make debugging hard, but ultimately since most vendors support
4 byte ASN, then they should have an upgrade plan. :-)  There will be the
requirement to renumber the adjacency after upgrade too...

Since the AS4_PATH attribute is transitive, then 16-bit-only transit
networks will not destroy the 4-byte as path for other 32-bit speakers.


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