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
