Help with DHCPv6 client-identifiers

[sthaug at nethelp.no]

> > 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.
> 
> Then it is indeed fortunate that DHCPv6 doesn't do what you want.   Using prefixes wider than /64 breaks IPv6.   That's why SLAAC doesn't do it.

Of course using prefixes wider than /64 doesn't break IPv6. It breaks
SLAAC, which is not at all the same thing. You, of all people, should
know this.

For our uses, SLAAC simply doesn't cut it - so we end up using RA plus
DHCPv6. I can bitch and moan about what I think is a bad design - making
DHCPv6 dependent on RA. But at the end of the day I can live with RA and
DHCPv6.

However, the decision to make it impossible to get the MAC address of
the client through DHCPv6, I think, is completely inexcusable, and needs
to be fixed.

Steinar Haug, Nethelp consulting, sthaug at nethelp.no