DHCP, Dynamic DNS, and IPv6

[David W. Hankins]

On Wed, Aug 27, 2008 at 05:26:50PM -0700, Loren M. Lang wrote:
> I am considering switching/complementing IPv6 auto-configuration which
> the IPv6 version of DHCP.  I assume it supports Dynamic DNS is the same
> manner as with IPv4.  Will the two daemons clash when assigning names
> under the same domain?

I'm confused as you say 'IPv6 auto configuration' and then 'ISC DHCP
IPv6 support'.  I'll answer two questions then;

SLAAC, as from Router Advertisements, doesn't support DDNS.  It is a
broadcast query/response protocol, where one reply by the 'server'
(router) configures many clients.  It has no way of knowing what names
the clients want, as it will not hear from all of them, nor does it
know what addresses the names are assigned to, as the clients choose
those.

It is possible that someone might write a DDNS updates for SLAAC
clients, but then you have a key distribution problem or a diminished
benefit from automation ("manually configuring your clients to
automatically configure themselves").


ISC DHCPv6 does support the DHCPv6 FQDN option and Dynamic DNS
Updates, configuration is precisely the same as with DHCPv4.  As I
looked at the sources recently, there is one wrinkle (bug); when the
AAAA's expire, it will remove the last DHCID if there are no more
AAAA's (assigned by other servers).  It needs to check that there are
also no more A's.  Repairing this is a SMOP, look to
"^ddns_remove_fwd" in common/dns.c, and the section of code headed by
"A RR does not exist".  Simply make this two explicit PREREQs for no
A and no AAAA (opcode = NXRRSET), rather than one for the prescribed
"ddns_address_type".

-- 
Ash bugud-gul durbatuluk agh burzum-ishi krimpatul.
Why settle for the lesser evil?	 https://secure.isc.org/store/t-shirt/
-- 
David W. Hankins	"If you don't do it right the first time,
Software Engineer		     you'll just have to do it again."
Internet Systems Consortium, Inc.		-- Jack T. Hankins