AT&T UVERSE Native IPv6, a HOWTO

Thu Nov 28 23:40:11 UTC 2013

On 28 November 2013 14:56, Mark Andrews <marka at isc.org> wrote:
>
> In message <CAPKkNb6Nhr-bcvkTwTjf+rFovhYjv0+xyCPM6D4CndvZn3FqeA at mail.gmail.com>
> , "Constantine A. Murenin" writes:
>> On 28 November 2013 13:07, Leo Vegoda <leo.vegoda at icann.org> wrote:
>> > Andrew D Kirch wrote:
>> >
>> > Was I the only one who thought that everything about this was great
>> > apart from this comment:
>> >
>> >> In reality additional poking leads me to believe AT&T gives you a
>> > rather
>> >> generous /60
>> >
>> > Is a /60 what is considered generous these days? I thought a /48 was
>> > considered normal and a /56 was considered a bit tight. What prefix
>> > lengths are residential access providers handing out by default these
>> > days?
>>
>> Remember, this is just 6rd.  With 6rd, a /60 does sound quite generous indeed
>> .
>
> You can hand out /48 as easily with 6rd as you can natively.
>
> It's only when the ISP is lazy and encodes the entire IPv4 address
> space into 6rd thereby wasting most of the IPv6 address space being
> used for 6rd that a /60 appears to be generous.
>
> You can do a 6rd domain per IPv4 allocation.  This is a one time
> operation that doesn't need to be updated as you move IPv4 address
> space around.

This might be true with smaller ISPs, but someone like AT&T probably
already has too many distinct IPv4 allocations for such an encoding to
be practically manageable.

Free, who has pioneered 6rd, and is a major ISP in France, seems to
have gone with a similar 6rd allocation policy, giving out /60 through
6rd for each IPv4, out of a /28 IPv6.  Seems quite reasonable.

    http://ripe58.ripe.net/content/presentations/ipv6-free.pdf

(So, AT&T simply copied the French here, it would appear.)

C.

>
>> And it's a /60 for each IPv4 you have, e.g. if you have a static IP
>> allocation with AT&T U-verse, say, a /27, then you're effectively
>> getting a /55 (plus also an additional /60 for the DHCP address in a
>> shared subnet to which your /27 is routed to).
>>
>> That said, I wholeheartedly agree with your comment otherwise.
>>
>> C.
>>
> --
> Mark Andrews, ISC
> 1 Seymour St., Dundas Valley, NSW 2117, Australia
> PHONE: +61 2 9871 4742                 INTERNET: marka at isc.org