IPv6 static IP address

[Graham Clinch]

Hi Hans,

> We are using ISC dhcp version 4.3.3 with Cisco router and we try to implement IPv6. So far IPv4 is working well and with IPv6 it's fine with dynamic IP addresses and dynamic DNS updates are also working fine. But sometimes we want to assign static IP addresses. As well for V4 as for V6.
> With IPv4 I have done this since several years. It's easy. I can read the MAC address from the lease file and can make an entry in dhcpd.conf 

'hardware ethernet' also works for DHCPv6 (from 'Changes since 4.1.0 (new features)' in the release notes):

- The 'hardware [ethernet|etc] ...;' parameter in host records has been
  extended to attempt to match DHCPv6 clients by the last octets of a
  DUID-LL or DUID-LLT provided by the client.

And RFC 6939 support was added in 4.3.4 (from 'Changes since 4.3.3' in the release notes):

- The server will now match DHCPv6 relayed clients to host declarations
  which include the "hardware" statement, if the relay connected to the
  client supplies the client's hardware address via client-linklayer-address
  option as per RFC 6939.
  [ISC-Bugs #40334]

So if you know the hardware address from IPv4, you can add a similar host declaration for v6 without worrying about the duid (unless you want to).

Some DHCP clients can send the v6 DUID as the v4 client identifier, so rather than matching on hardware address you match both on client identifier.  This seems to have been the original intention in the specifications, but the real world doesn't seem to be working that way.

Graham