DDNS with multiple primary DNS servers

[Ingen Schenau, Jeroen van (ICTS)]

Hi,

I recently started with dynamic DNS, using dhcpd to dynamically update a
DNS zone in BIND. There are some excellent tutorials on the web, so it
was relatively easy to implement.

There's only one thing I can't get working yet: we have two primary
(master) DNS servers and only the first server is updated. So all our
zones are defined on two DNS servers, both master, with virtually
identical configs built from a database.

I listed both servers in the config; dhcpd.conf snippet:

zone roaming.mydomain.example {
  primary 10.0.0.2, 10.0.0.3;
  key dhcp_updater;
}

While the dhcpd.conf manpage doesn't say anything about multiple
primaries, the comments in the source (common/dns.c) indicate that it
should be supported:

 * The way this works is that you define the domain name to which an
 * SOA corresponds, and the addresses of some primaries for that domain
name:
 *
 *      zone FOO.COM {
 *        primary 10.0.17.1;
 *        secondary 10.0.22.1, 10.0.23.1;
 *        key "FOO.COM Key";
 *      }
 *
 * If an update is requested for GAZANGA.TOPANGA.FOO.COM, then the name
 * server looks in its database for a zone record for
"GAZANGA.TOPANGA.FOO.COM",
 * doesn't find it, looks for one for "TOPANGA.FOO.COM", doesn't find
*that*,
 * looks for "FOO.COM", finds it. So it
 * attempts the update to the primary for FOO.COM.   If that times out,
it
 * tries the secondaries.   You can list multiple primaries if you have
some
 * kind of magic name server that supports that. 


So I was wondering: does anyone use DDNS with a "multi master" DNS setup
or are we just weird for trying such a thing? Is it supported or not and
might this be a bug?

I tested with dhcpd 4.2.1 built from source; I'm afraid my C skills are
limited so I'm not sure how to analyze/debug this further myself. I'd
appreciate any insights you dhcpd-gurus might offer ;)


By the way: while it's theoretically possible to change the setup for
our "roaming.mydomain.example" zone to a master/slave config, it would
be hard to fit into our config build procedures. So if possible I prefer
to dynamically update two DNS servers from DHCP.


Regards,

Jeroen van Ingen
ICT Service Centre
University of Twente, P.O.Box 217, 7500 AE Enschede, The Netherlands