Minimum IPv6 size

Fri Oct 2 23:43:14 UTC 2009

> Date: Fri, 02 Oct 2009 16:29:25 -0700
> From: Seth Mattinen <sethm at rollernet.us>
> 
> Since we're on the topic of what's commonly accepted in IPv4 land (a
> /24), what's the story in IPv6 land? It seems to me that a /32 is a fur
> sure thing, but others will accept down to a /48, too.

Depends on the address space it is assigned from. Most specify a maximum
prefix length of 32, but the micro-allocations and the allocations for
PI dual-homing are /48.
We consider the following to be "legal":
                /* global unicast allocations */
                route-filter 2001::/16 prefix-length-range /19-/35;
                /* 6to4 prefix */
                route-filter 2002::/16 prefix-length-range /16-/16;
                /* RIPE allocations */
                route-filter 2003::/18 prefix-length-range /19-/32;
                /* APNIC allocations */
                route-filter 2400::/12 prefix-length-range /13-/32;
                /* ARIN allocations */
                route-filter 2600::/12 prefix-length-range /13-/32;
                /* ARIN allocations */
                route-filter 2610::/23 prefix-length-range /24-/32;
                /* LACNIC allocations */
                route-filter 2800::/12 prefix-length-range /13-/32;
                /* RIPE allocations */
                route-filter 2A00::/12 prefix-length-range /13-/32;
                /* AfriNIC allocations */
                route-filter 2C00::/12 prefix-length-range /13-/32;
                /* APNIC PI allocations */
                route-filter 2001:0DF0::/29 prefix-length-range /40-/48;
                /* AFRINIC PI allocations */
                route-filter 2001:43F8::/29 prefix-length-range /40-/48;
                /* ARIN PI allocations */
                route-filter 2620::/23 prefix-length-range /40-/48;
                /* ARIN Micro-allocations */
                route-filter 2001:0500::/24 prefix-length-range /44-/48;

This means accepting prefixes ARIN says we should not, but ARIN does not
set our routing policy and I will be on a panel on that issue at NANOG in
Dearborn later this month.
-- 
R. Kevin Oberman, Network Engineer
Energy Sciences Network (ESnet)
Ernest O. Lawrence Berkeley National Laboratory (Berkeley Lab)
E-mail: oberman at es.net			Phone: +1 510 486-8634
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