Using DHCP only for DNS in IPv6

David W. Hankins dhankins at
Thu Mar 18 23:31:24 UTC 2010

On Wed, Mar 17, 2010 at 08:48:24PM +0000, Paul Selkirk wrote:
> > I understand that it should be possible to use stateless 
> > autoconfiguration with e.g. radvd in IPv6 to allocate addresses and 
> > routing information, while using DHCP only for DNS, NTP etc.
> > 
> > Is this possible in ISC dhcp ?
> dhclient -6 -S
> -S was added in 4.1.0.

Or if you're asking about the server, it's no different from
configuring for "stateful" DHCPv6, just don't include a dynamic pool
range if you don't want to allocate addresses.

Be sure to track 4.0 or 4.1 maintenance and not one of the .0 releases
because there was a messy configuration thing we cleaned up that made
stateless configuration harder to understand (shared-network thing).

> > If so, can one use DDNS to update BIND with the client address ?
> `man dhclient.conf` and/or `man dhcpd.conf`, look for the sections on
> Dynamic DNS.

Note that any kind of DDNS requires a protocol mechanic that implies
a "request for a given specific resource" and an unambiguous reply
granting that resource with an expiration time for cleanup.
Allocating a domain name to a client is no different from allocating
an address in that sense.

So any attempt to get DDNS updates done by the "server side
infrastructure", e.g. in the radvd responding to Solicits or in a
DHCPv6 server responding to Information-Request messages is doomed to

For DDNS in a DHCPv6 context I think you need to run stateful
allocation.  I don't know or remember if our client will try to use
an FQDN assigned in stateless/Information-Request to perform a DDNS
update on its own, if it is configured to.

So far as I'm aware the only DDNS solution in stateless allocation is
to perform the DDNS on the client directly; configure the client to
perform DDNS to record its name once it has finished DAD.  We don't
have a tool that does that, but it wouldn't be hard to write a shell
script using BIND's 'nsupdate' utility.

David W. Hankins	BIND 10 needs more DHCP voices.
Software Engineer		There just aren't enough in our heads.
Internet Systems Consortium, Inc.
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