On 16/03/15 17:13, Nick Hilliard wrote:
On 16/03/2015 17:03, David Wilkinson wrote:
I am looking at setting up some BGP communities and I was wondering what is
the correct/recommended way to do communities with a 32-bit ASN?
Obviously I can't use the asn:nn format with our 32-bit ASN, So would I use
private ASNs or AS23456 or should I be looking at using extended communities?
I am looking at doing the usual stuff adding communities to incoming routes
from transits, peers, customers. Allowing customers to block announcements
out via a transit provider/peer. Setting up a black hole community, etc
The shorter answer is that you are far better off renumbering your ASN.
It's painful, but it's a lot less painful than pretending you can fix this
on your network and realising later on deciding that this is pointless and
then renumbering.
The longer answer is that the IETF has not yet dealt with this situation
and the various working groups involved are in mild to total denial that a
problem exists. Extended BGP communities have been put forward as a
candidate (RFC 5668), but support on router platforms is fairly limited at
the moment. It also only support 32b:16b style ASNs, so if you plan to
use the local administrator field for anything, then you'd better be able
to fit it into 16 bits. There is some talk about a kitchen sink BGP
community mechanism (draft-raszuk-wide-bgp-communities), but in the last 4
years it hasn't progressed beyond talk.
Nick
That might explain why my searches didn't come up with much about it.
How annoying.
I will take a look at seeing what is involved with renumbering the ASN
and see what we decide to do.
Regards
David
