DDNS with multiple primary DNS servers

[Ingen Schenau, Jeroen van (ICTS)]

Hi,

> >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.
> 
> Both of those are show stoppers - period.
> 
> Firstly, DHCPD will only update a single server, and relies on that 
> to send updates to the other servers. Since DHCPD was written at ISC, 
> and ISC BIND already has a good update mechanism for multiple servers 
> then I think it's easy to see why they'd avoid the duplication and 
> complexity* of updating multiple servers directly from the DHCP.
> * It doesn't take too much thought to see that updating multiple 
> servers, with all the permutations of success and failure possible, 
> would quickly get complicated and/or inefficient and/or error prone.

That's a good point, error handling and remaining consistency (as Glenn
also points out) would be quite hard.

Then perhaps multi-master updates haven't been implemented for good
reasons, contrary to what the source comments suggest.


> Secondly, dynamic updates assume a DNS model with dynamic zone 
> contents. This is fundamentally incompatible with a zone generated 
> from an outside source unless you also allow updates from the DNS 
> server back into the source (database in this case).

True. In our specific case, this one zone would never be fed from or
stored back to the database, but the configuration with the zone
definition (and whether the servers are master or slave) is generated
equally for all servers.


> In theory you could "do your own thing" by using "on event" triggers 
> in DHCPD to call your own scripts that will do the updates. I have no 
> idea how easy (or otherwise) this would be.

I wouldn't feel comfortable with "on event" triggers and external
nsupdate calls for this functionality.

Thanks for your insights (and Glenn, thank you too!). We'll concentrate
on changing our DNS config scripts, so we can do master/master for all
static zones and master/slave for the dynamic part.


Regards,

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