On Wed, Oct 8, 2014 at 10:48 PM, James R Cutler <james.cutler@consultant.com> wrote:
On Oct 8, 2014, at 9:18 PM, Erik Sundberg <ESundberg@nitelusa.com> wrote:
I am planning out our IPv6 deployment right now and I am trying to figure out our default allocation for customer LAN blocks. So what is everyone giving for a default LAN allocation for IPv6 Customers. I guess the idea of handing a customer /56 (256 /64s) or a /48 (65,536 /64s) just makes me cringe at the waste. Especially when you know 90% of customers will never have more than 2 or 3 subnets. As I see it the customer can always ask for more IPv6 Space.
/64 /60 /56 /48
Hi Erik, You're asking the right question and you understand the divisible-by-four rule for prefix delegation, which is good. The answer I recommend is: 1. Nothing smaller than /56 unless you know enough about the situation to be sure /56 is unnecessary. In particular, never provide a /64 to a customer... delegate nothing between /61 and /123, ever. You'll just be making mess that you have to clean up later when it turns out they needed 3 LANs after all. 2. Suggest /56 for residential and /48 for business customers as default, didn't ask for something else sizes. 3. /48 for anyone who makes the effort to ask, including residential customers. 99% won't ask and won't care any time in the foreseeable future. 4. Referral to ARIN for anyone who requests more than a /48. If they have a good reason for needing more than 65,000 LANs that reason is likely good enough to justify a direct ARIN assignment. If they don't have a good reason, the experience will teach them that without needing to get them mad at you.
Selection of a default prefix is easy. Here are the steps.
4. Keeping in mind
4.1 Prefixes longer than somewhere around /48 to /56 may be excluded from the global routing table
4.1a Prefix cutouts of any size (including /48) from inside your /32 or larger block may be excluded from the global routing table. Folks who are multihomed and thus need to advertise their own block with BGP should be referred to ARIN for a direct assignment. Folks who aren't multihomed, well, until given evidence otherwise I claim there are no single-homed entities who will use 65,000 LANs, let alone more.
4.2 Your customers want working Internet connections 4.3 You want income at a minimum of ongoing expense
make a sensible business decision.
IPv6 is large but not infinite. No need to be conservative, but profligate consumption is equally without merit. Regards, Bill Herrin -- William Herrin ................ herrin@dirtside.com bill@herrin.us Owner, Dirtside Systems ......... Web: <http://www.dirtside.com/> May I solve your unusual networking challenges?