dynamic dns server?

Craig craig5 at pobox.com
Thu Mar 15 22:03:03 UTC 2007

Simon Hobson wrote:
> Craig wrote:
>> But, which DNS server is dhcpd going to try to update?
> If you specified a zone declaration in the dhcpd.conf file then it 
> will use the specified server. If not then it will use the correct 
> server.

"zone decl"??? If I "man dhcpd.conf" the only "zone" that is referred to
is in named.conf. Can you be a little more specific?

> "correct server" is the authoritative server listed in the zones SOA 
> record - so if your dns is correctly set up then it will all happen 
> automagically. Of course, if you have bogus data in your dns then the 
> dhcp server will attempt to update the wrong place.

Crap, that's what I thought. I left out some details.

Currently, all of the machines are in the domain "example.com". we are
trying to create some sub-domains: "servers.example.com",
"desktops.example.com", etc. So, those sub-domains only exist in the
"internal server" ( and not on the external (ISP) servers:

So, there is no way to the OS on the dhcp server to figure out who is
authoritative for the new subdomains (eg servers.example.com).

>> option domain-name-servers x.y.z.1, x.y.z.2, x.y.z.3;
>> Where x.y.z.0 is NOT our network. We have a DNS server at
>> How does dhcpd decide which dns server to try to update?
> See above
>> Also, how do I tell dhcpd to update and NOT any of the
>> x.y.z.* servers?
> Is authoritative for the zones ?

Yes, but it ( is NOT listed in the dhcp server's resolv.conf.
(I was trying to get dynamic dns all working before enabling it on our

I was hoping that there was a config option in dhcpd that said "update
this server". But, in retrospect, if DNS is all set up properly, that
would be completely redundant since that information can be obtained
from DNS...

> All this is, of course, as "as seen by the dhcp server" which will 
> consult the servers specified in your resolv.conf file to find the 
> SOA record for the zone being updated.

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