IPv6 Default Allocation - What size allocation are you giving out

Baldur Norddahl baldur.norddahl at gmail.com
Thu Oct 9 07:58:56 UTC 2014

We assign a /128 by DHCPv6 (*). And then we assign a /48 by DHCPv6-PD
prefix delegation. To everyone no matter what class of customer they are.

You are thinking about it wrong. It is not about what the customer need but
about what you need. Do you really have a need to use more than 48 bits for
your routing? Do we need more than 48 bits for the global routing table? Do
we need more than 48 bits to conserve enough address space for any
conceivable future setting? The answer is no to all of these, so why are
you trying to decide what a user could be doing with the remaining address

What if IPv6 had been designed with a variable address length, such that
you could do 2048 bits addresses if you wanted. What prefix length would
you choose if that was the case? Where do you stop? Would you really be
giving out /1024 because otherwise it would be "wasteful"? No, I believe
you would be giving out /48s.

(*) using /128 on the subscriber link solves a security issue and makes
deployments on asymmetric links easier. Again we are doing it because of
operational issues and not because we are trying to conserve address space.



On 9 October 2014 03:18, Erik Sundberg <ESundberg at 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
> Small Customer?
> Medium Customer?
> Large Customer?
> Thanks
> Erik
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