Some comments on the point provided by Egbert, DD9QP:
- on the EU Hamnet, extant AS' are actually 32 bit with leading bits 0. The implementation which is used in the Mikrotik router is "New" BGP - LU has used initially 42x private AS' but now has its own real AS, 15780, nothing has changed in this case except peering definition - My router interoperates without issues with LU using 4222620001 while LU uses 15780 - both use MT equipment like the EU Hamnet - on the same time it uses old style peering with DE, without problems
I don't think that for implementing these AS numbering scheme, there is any need to change anything in the established 16bit-like BGP peers, except proper 32bit peer setup as they build up.
73s, Marius