On Wed, 2011-06-15 at 01:06 +0200, Ondrej Zajicek wrote: > On Sat, Jun 11, 2011 at 11:57:54AM +0200, Laurent GUERBY wrote: > > Hi, > > > > One of our BPG4 peer is asking us to send directly an AS4 open message > > instead of going through transitional AS23456. We run a 32 bits ASN > > and our peer has a 16 bits ASN. > > > > If my reading of documentation and BIRD source code (1.2.5 and 1.3.1) is > > correct BIRD only starts using AS4 if the peer advertise the AS4 > > capability in its open message. > > > > << > > p->as4_session = conn->want_as4_support && conn->peer_as4_support; > > > > conn->want_as4_support = conn->bgp->cf->enable_as4 && (conn->start_state > > != BSS_CONNECT_NOCAP); > > conn->peer_as4_support = 0; // Default value, possibly changed by > > receiving capability. > > > > case 65: /* AS4 capability, RFC 4893 */ > > if (cl != 4) > > goto err; > > conn->peer_as4_support = 1; > > >> > > > > Our peer open doesn't currently send the AS4 capability in its open > > message so we're stuck for now. > > > > I don't know if hardware and software BGP4 implementations other than > > BIRD have this capability and what are the true implications of this > > request. > > I am not sure what exactly is requested. 32 bit ASNs cannot be sent > directly in an OPEN message in its ASN field, they are always sent as a > part of an AS4 capability. You could check that (that an AS4 capability > is attached in your OPEN message) using tcpdump. If your peer does not > send AS4 capability that probably means (unless it is misconfigured) > that it does not support AS4 and you cannot establish AS4-style session, > but old-style BGP session should be established.
Hi, Thanks for the clarification, I reached the same conclusion reading the RFCs. tcpdump shows that BIRD is sending OPEN with the AS4 capability so I will contact our peer again. Sincerely, Laurent
