It's Ars Tech's turn to bang the IPv4 exhaustion drum

Nathan Ward nanog at
Tue Aug 19 12:36:33 CDT 2008

On 20/08/2008, at 5:25 AM, Michael Thomas wrote:
> Justin M. Streiner wrote:
>> On Tue, 19 Aug 2008, michael.dillon at wrote:
>>>> I don't have a problem with assigning customers a /64 of v6
>>>> space.
>>> Why so little? Normally customers get a /48 except for residential
>>> customers who can be given a /56 if you want to keep track of
>>> different block sizes. If ARIN will give you a /48 for every
>>> customer, then why be miserly with addresses?
>> I don't operate an ISP network (not anymore, anyway...).  My  
>> customers are departments within my organization, so a /64 per  
>> department/VLAN is more sane/reasonable for my environment.
> Uh, the lower 64 bits of an IP6 address aren't used for routing you
> know? They're essentially the mac address, or some other sort of
> autoconf'd host identifier. Last I heard, the smallest allocation is
> supposed to be a /48 -- I hadn't heard of the /56 thing that Michael
> was speaking of, though I'm not surprised. There's 64 bits for
> routing... no need to be so stingy :)

64 bits is not a magical boundary.

112 bits is widely recommended for linknets, for example.

64 bits is common, because of EUI-64 and friends. That's it.
There is nothing, anywhere, that says that the first 64 bits is for  

Nathan Ward

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