Linux source address selection vs. EUI-64

Brian E Carpenter brian.e.carpenter at
Sun Nov 14 04:42:23 CET 2010


>From your later message I understand a bit better what your scenario is.
Yes, in the case of a rack full of virtual hosts, shoving
them all in one subnet makes sense, but longer than /64 seems certain
to create problems unless you redesign SLAAC.


On 2010-11-14 16:35, Brian E Carpenter wrote:
> On 2010-11-14 04:32, Eugen Leitl wrote:
>> On Sat, Nov 13, 2010 at 03:36:57PM +0100, Geert Hendrickx wrote:
>>> For individual hosts (esp. in a VPS environment), assigning a /64 or
>>> larger makes little sense to me, a /96 is more than enough.
>> Is that an official recommendation? I currently have a single /56,
>> which I would like to distribute over several thousands customers,
>> each on a virtual server, with currently one static IPv4 address.
> It is certainly not. /64 should really be the longest. Firstly
> it's assumed by SLAAC and secondly you can't possibly know whether
> a customer wants to subnet. A /56 would be a better default per
> customer, in case they want multiple subnets. How can you possibly
> tell what a customer will do if they hook up building automation
> systems for example.
> This is why we designed IPv6 in the first place!
> *Please* see
> which is on the way to being a recommendation.
>    Brian
>> I can see how a /96 for each customer would be more than enough
>> (especially that since hundreds of customers are going to share
>> the same MAC, due to the low-overhead virtualization technology
>> used). 
>> Presumably, in above context it would be a sane thing to parcel 
>> the /56 into /64, each for one physical server's distinct NIC 
>> MAC, and from each /64 a /96 for each virtual server?

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