DHCP server does not update DNS

Simon Hobson dhcp1 at thehobsons.co.uk
Thu Dec 22 07:57:37 UTC 2011

Richard Allen wrote:

>However I did have a
>thought while reading up on the interim method.  Here is a quote from the
>dhcpd.conf man page:
>        In addition to these differences, the server also does not update
>very aggressively.  Because
>        each  DNS  update  involves  a  round trip to the DNS server, there
>is a cost associated with
>        doing updates even if they do not actually modify the DNS
>database.    So  the  DHCP  server
>        tracks  whether  or  not it has updated the record in the past (this
>information is stored on
>        the lease) and does not attempt to update records that it thinks it
>has already updated.

Yes, that's what Glenn mentioned.

>Now, I don't know how to read the leases file, but is there any chance dhcpd
>thinks the client has already registered and thus does not try to do it again?

It's not in the lease you quoted. If a DNS update has already been 
done, then you'll see entries for (from memory) something like 
"ddns-hostname" and "ddns-<something-else>"

>I really wish there was an option to make dhcpd aggressive with it's DNS
>updates... :)

That won't help while you have your current problem.

Just a thought ...
The Windows machines, are they managed via AD and group policies ? 
I'm just wondering if there's something in that that's overriding the 
DHCP options ?

Simon Hobson

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