I think you will learn a lot of /128s from IGP, but not from eBGP. I consider the "wild" to be the DFZ or similar type of network and in that case, you should not see advertisements for anything longer than a /48. This is not hard and fast, but please correct me if I'm wrong.
- Brian J. >-----Original Message----- >From: Mark Tinka [mailto:mti...@globaltransit.net] >Sent: Thursday, December 15, 2011 12:30 AM >To: nanog@nanog.org >Subject: Re: /128 IPv6 prefixs in the wild? > >On Thursday, December 15, 2011 01:54:56 PM Glen Kent wrote: > >> In an IP/MPLS world, core routers in the service provider >> network learn the /32 loopback IPv4 addresses so that >> they can establish BGP/Targetted LDP sessions with >> those. > >That's right - not sure how things would have been if >'draft-swallow-mpls-aggregate-fec-01' had gained some >traction. > >> They then establish LSPs and VPN tunnels. > >Indeed. > >> Since >> we dont have RSVP for IPv6 and LDP for IPv6 (not yet >> RFC) we cannot form MPLS tunnels in a pure IPv6 only >> network. GIven this, would v6 routers have large number >> of /128 prefixes? >> >> What are the scenarios when IPv6 routers would learn a >> large number of /128 prefixes? > >I suspect ISP's that choose to assign broadband customers >/128 addresses because "they only ever need one address" may >be a situation where you see rise given to this. > >> I would presume that most IPv6 prefixes that the routers >> have to install are less than /64, since the latter 64 >> is the host part. Is this correct? > >This is certainly going to re-open some "wounds", but no, >not all providers are assigning /64 to interfaces. Some >(like us) are using longer prefix lengths such as /112 and >/126. > >But as for /128 prefix lengths, aside from the fact that >Loopbacks will be floating around the network, whether >you're using them to signal MPLS LSP's or setup iBGP >sessions, you will see them with ISP's that assign them to >customers and choose not to aggregate them at specific edge >routers. > >Cheers, > >Mark.
