Help with DHCPv6 client-identifiers

[Alex Bligh]

--On 19 November 2011 09:27:55 +0100 Simon Hobson <dhcp1 at thehobsons.co.uk> 
wrote:

>> Autoconfig is quite inflexible in terms of addressing and netmasks which
>> can be used. In particular, use of EUI64 means you end up giving the
>> client a much bigger subnet than they need, and it is hard to allocate
>> >1 IPv6 address per NIC (i.e. per MAC) using this scheme without wasting
>> yet more space. What we'd really like is to be able to allocate a fixed
>> number of least significant bits (say 24) as "index of IP on one NIC",
>> then the next (say 24) as "index of NIC on vLAN". Each vLAN would then
>> get a /80. We could do have done that with DHCP or similar if it worked.
>
> Ahh, I recognise this. You want pattern and consistency (much as I do in
> my networks). In effect, you want to be able to look at an address, drop
> a few bits, and effectively have something that identifies a customer's
> machine(s). The alternative being that the only way to tell them apart
> form others is to look them up in the database **every** time.
>
> Unfortunately, or fortunately depending on how you look at it, IPv6 is
> going to force people to fix their DNS (and management systems).

For us, it's actually more about allocation policy. We don't remember 
anything because it's all in databases, so there are no "RainMan" problems. 
However, at the time of allocation we have no idea what the maximum number 
of IPs per NIC or NICs per subnet is, so have to assume they are large (and 
IPv6 was meant to free us from renumbering). EUI64 makes for an inefficient 
use of space.

-- 
Alex Bligh