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Re: Assigning IPv6 /48's to CPE's?

  • From: William Herrin
  • Date: Mon Dec 31 22:11:10 2007
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On Dec 31, 2007 3:25 AM, Rick Astley <[email protected]> wrote:
> I can understand corporations getting more than a /64 for their needs, but
> certainly this does not mean residential ISP subscribers, right?


The standing recommendations are:
* /32 for ISPs unless they can justify more
* /48 for subscribers unless they can justify more
* /64 when you know for certain that one and only one subnet will ever
be required
* /128 when you know for certain you're dealing with a single device
* Sparse allocation so whichever size you choose you can usually
increase it by simply changing the prefix length.

Some folks also suggest:

* /56 for small customers (residential DSL and similar "always on" services)

But the real answers to your question are:

1. Be flexible. A /64 is four billion times less valuable than a
single IPv4 address. If the customer tells you he wants a /56 or even
a /48, just give it to him. At the /48 level, the customer is vastly
more valuable than the addresses.

2. The world won't end if you assign /64's to traditional dynamic IP
address residential customers and replace them with a /56 or /48 on

3. The world won't end if you assign one of your 16 million /56's to
each customer up front.

4. No one has enough operational experience with IPv6 to know what the
right answer will turn out to be here, so do what makes you happy and
plan to adjust it later.

Bill Herrin

William D. Herrin                  [email protected]  [email protected]
3005 Crane Dr.                        Web: <>
Falls Church, VA 22042-3004