On Wed, Jan 16, 2013 at 2:53 PM, fredrik danerklint <fredan-nanog@fredan.se> wrote:
ARIN and IETF cooperated last year to allocate 100.64.0.0/10 for CGN use. See RFC 6598. This makes it possible to implement a CGN while conflicting with neither the user's RFC1918 activity nor the general Internet's use of assigned addresses. Hijacking a /8 somewhere instead is probably not a great move.
If I have calculated the netmasks right that would mean to set aside:
2001:0DB8:6440::/42
for the use of 6rd service:
2001:0DB8:6440:0000::/64 = 100.64.0.0 .... 2001:0DB8:647F:FFFF::/64 = 100.127.255.255
Sander already touched on this, but when implementing 6rd you'll want *at least* 4 bits on the subnetting side of the IPv6 block associated with each IPv4 address and you'll want that netmask to be evenly divisible by 4. A /60 or a /56, not a /64. In IPv4 your customer has a "DSL router," potentially with distinct wired and wireless LANs running different RFC1918 address blocks. In IPv6 each of those LANs will consume a /64, so he'll need more than one. Selecting a netmask evenly divisible by 4 has two major benefits. First, it exactly matches one character in the written address. The customer doesn't have ...:ABC4:* through ...:ABC7:*, he has ...:ABC*::. Second, each delegable RDNS zone takes up the same 4 bits so the assignment will be right on an RNDS zone boundary.
Even tough you have very good arguments, my suggestion would be to have a class A network (I got that right, right?) for all the users and only having 6rd as service on that network.
I assume you meant this a little differently than what you wrote here. It wouldn't make any kind of sense to stand up a private IPv4 network with no IPv4 Internet connection in order to facilitate IPv6 via a 6rd deployment. For one thing it'd be a Rube Goldberg machine. For another, I suspect you'd find it very challenging to acquire a threshold number of paying customers for an IPv6-only network at the moment. Regards, Bill Herrin -- William D. Herrin ................ herrin@dirtside.com bill@herrin.us 3005 Crane Dr. ...................... Web: <http://bill.herrin.us/> Falls Church, VA 22042-3004