DDNS with multiple primary DNS servers

Simon Hobson dhcp1 at thehobsons.co.uk
Tue Jun 21 14:04:54 UTC 2011

Ingen Schenau, Jeroen van (ICTS) wrote:

>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.

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).

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.

Simon Hobson

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