Where to buy Internet IP addresses

Mark Smith nanog at 85d5b20a518b8f6864949bd940457dc124746ddc.nosense.org
Tue May 5 08:13:29 CDT 2009


On Tue, 05 May 2009 13:04:49 +1000
Karl Auer <kauer at biplane.com.au> wrote:

> On Tue, 2009-05-05 at 04:49 +0200, Randy Bush wrote:
> > > I'm with you.  I wish vendors and spec designers would just get over it  
> > > and let people subnet however they want.
> > [...]
> > do other than 64 and you do not get auto-conf.  some do not consider
> > this a loss, others do.
> 
> This is an important distinction.
> 
> - you CAN subnet however you like, with any number of bits in
>   your prefixes
> 
> - autoconfiguration will work only in subnets with a 64 bit prefix.
> 
> The two matters are quite independent of each other, as far as I can
> tell.
> 

Older protocols, like classful IPv4, Appletalk etc. put a hard boundary
between the network and node portion. That was simple and, in the case
of IPX, Appletalk and DECNET, it was very convenient to have fixed
length network and node portions. IPv4 originally had a single boundary
between the network and node portion - if you look up the early
RFCs/IENs, the IPv4 addressing format was similar to Class A.

Of course in the case of IPv4, those classful hard boundaries caused
problems when we needed to squeeze more addresses out of the 32 bits by
moving to a fully varying boundary between the network and node
portions. IPv4 software in all nodes needed to be upgraded to work.

I think of the way IPv6 has done it is the middle ground. For
forwarding, the boundary between the network and node portions isn't
hard - it's purely longest match on the whole 128 bits. However, because
we've got so many bits, within a portion of the address space, a harder
(but not hard) boundary exists, to benefit from the convenience of
having fixed length node addresses, which results in things such as much
simpler autoconfiguration etc.

Regards,
Mark.





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