[CentOS] IPV4 is nearly depleted, are you ready for IPV6?

Tue Dec 7 20:31:15 UTC 2010
Lamar Owen <lowen at pari.edu>

On Tuesday, December 07, 2010 12:39:28 pm Les Mikesell wrote:
> > How many devices?  You mean exceeding the number of available inside a
> > IPv6 subnet?  I do hope you're kidding ... as for a /64 subnet we're
> > talking about 4.294.967.296 addresses doubled 32 times.
> Is that what people will automatically get in a home ISP connection?

Abbreviations: PI = Provider Independent, PA = Provider Assigned, RIR = Regional Internet Registry, ARIN = American Registry of Internet Numbers, BGP = Border Gateway Protocol, AS = Autonomous System (the routing 'atom' at the BGP level), ASN = Autonomous System Number.

It will depend upon your provider if you get PA addresses; if you go straight to the RIR (ARIN for North America) and pay to get PI addresses you will get by default a /48; but then you have to get your provider to agree to advertise that /48 over BGP.  The IPv6 table has the potential to be vastly larger than the IPv4 table (the number of /48's in IPv6 is 65,536 times the total addresses in IPv4!)  One hopes providers will intelligently aggregate; until there is sane multihoming for enterprise endusers good aggregation is going to be elusive, since multihomed sites are going to desire PI space, which will fragment the routing tables.  IPv6 routing tables do require larger entries thanks to the four times larger address, after all, and with 32 bit ASN's the AS path for that table entry also doubles in size.

Having said that, most providers probably will give you one of a /48, /56, or /64.  There are plenty of addresses available, but if you ever have to renumber (like when changing providers).... you'll want PI, or ULA with NAT66 to PA.