[6bone] Is minimum allocation /64 now?

[Jesper Skriver]

On Fri, Oct 24, 2003 at 09:12:48AM +0300, Pekka Savola wrote:
> On Fri, 24 Oct 2003, Dan Reeder wrote:
> > Having read that rfc, howcome you suggest /112 or /64 rather than a /126 to
> > get around the anycast problem? The section 4.3 clearly states that the /126
> > will work fine - what is the point of suggesting a shorter prefix? To me
> > thats just wasteful addressing.
> 
> Uhh, please stop to think about it.  Even if we use /112's, we can have
> 2^48 of them, assigned from a single /64.  No ISP should need ever more
> point-to-point addresses than that :-).
> 
> Remember that "wasteful addressing" has entirely different meanings in
> IPv6 than IPv4.  Once you have an IPv6 /64, you can put as many nodes in
> that as you want, compared to e.g. an IPv4 /24.
> 
> /112 is a great simplification over /126 from the user's perfective.  This 
> is because with /126 you should use something like:
> 
> 3ffe:ffff:ffff::f00:{1,2}/126
> 3ffe:ffff:ffff::f00:{4,5}/126
> 3ffe:ffff:ffff::f00:{7,8}/126
> 3ffe:ffff:ffff::f00:{a,b}/126
> 3ffe:ffff:ffff::f00:{d,e}/126
> 3ffe:ffff:ffff::f01:{1,2}/126
> ....

But using a non /126 or /127 on a p2p link can result in a forwarding
loop, assume the the 2 routers have :1 and :2, and someone sends traffic
to :3, if the netmask is larger than /126, the routers will do a longest
match lookup, will find the interface prefix, and send the packet on the
p2p interface - unless they have a specific check to drop these packets.

/Jesper

-- 
Jesper Skriver, jesper(at)skriver(dot)dk  -  CCIE #5456

One Unix to rule them all, One Resolver to find them,
One IP to bring them all and in the zone to bind them.