What happens, if the IXP uses a 4-byte ASN? RFC5668 (4-Octet AS Specific BGP Extended Community) defines <Global Admin,4bytes>:<Local Admin, 2bytes>.
I have been asking some IXP operators, about their practice and their reply was "4-byte ASNs are supported by our RS". What's your experience? Did you see IXPs, that do not support them? Do you think, the IXP operators are aware of this limitation? Have you seen IXPs with 4-byte ASNs or do RIRs reserve 2-byte ASNs for future IXPs? What other operational problems did you experience while using 4-byte ASNs?
Do you see an issue with future IXP or future IXP members ? You can see at this list of members of one IXP that there are both 2-byte and 4-byte ASNs living in harmony, with a large number of 4-byte ones: http://ptt.br/particip/sp The IXP itself is using a 2-byte public ASN, so if at some point communities are used (although there are route-servers capable of granular policy without communities), they could use standard 2-byte community format. And with a bit coordination, 2-byte private ASNs and communities could be used to overcome limitations in member routers support of 4-byte ASNs. Rubens telnet lg.sp.ptt.br Trying 200.160.1.3... Connected to lg.sp.ptt.br. Escape character is '^]'. ============================================== = PTTMetro SP = = Contact: eng@ptt.br = = +55 11 5509-3550 = = inoc-dba: 22548*100 = = = = Looking Glass Server = = All connections and keystrokes logged = ============================================== lg.sp.ptt.br> show ip bgp summary BGP router identifier 187.16.218.252, local AS number 20121 RIB entries 32868, using 3081 KiB of memory Peers 4, using 18 KiB of memory Neighbor V AS MsgRcvd MsgSent TblVer InQ OutQ Up/Down State/PfxRcd 187.16.216.253 4 26162 3294906 1619885 0 0 0 05w0d23h 19247 187.16.216.254 4 26162 3468468 1617924 0 0 0 01w5d06h 19227 Total number of neighbors 2