IPv6, multihoming, and customer allocations

Sun Mar 14 05:49:18 UTC 2010

A couple of different incantations searching the archive didn't enlighten
me, and I find it hard to believe this hasn't been discussed.  Apologies and
a request for pointers if I'm rehashing an old question.

As a small/regional ISP, we got our /32 assigned and it's time to start
moving forward (customers are asking for it).  New hardware, updated IOS,
etc. are in the pipe.  Discussions are beginning with our upstream providers
for peering.  Now, what do we do?

A /48 seems to be the standard end-user/multi-homed customer allocation and
is the minimum allocation size from ARIN.  A /32 provides 65K /48s so, in
theory, we could give each of our customers a /48 and still have room for
growth.  A /48 also appears to be generally accepted as the the longest
prefix allowed through filters (although /49 through /54 are also
discussed).  Most customers, however, won't be multi-homed.

Partly from an IPv4 scarcity perspective, and partly from general efficiency
and thrift, it seems awfully silly to hand out /48s to somebody that may
have a handful of servers or a couple of home machines, especially with
special addressing like link-local if the hosts are not expected to be
internet reachable (back-end servervs, etc).

Based on the above, I'm looking to establish some initial policies to save
grief in the future:
- /52 allocations to end-users (residential, soho, etc.)
- /48 allocations to those that request it
- If you are going to multi-home, get your own space

This is obviously a very broad brush and takes an insanely large addressing
model and makes it even larger (assigning /52s instead of /48s) but, to me
at least, it seems reasonable for a first-pass.

 For context/scope, we currently have the equivalent of a bit more than the
equivalent of a  /16 (IPv4) in use.

Thanks,