dynamic update not working consistently

Jiann-Ming Su sujiannming at gmail.com
Thu Jan 7 19:38:16 UTC 2010


Okay, figured out the problem... In the dhcpd.conf man page it states:

   The ddns-updates parameter is on by default.

However, if you have a shared subnet declaration and one of the
subnets has "ddns-updates off" then all subnets under that shared
declaration has ddns-updates turned off.

So, in the example I gave, the working one was from a single subnet
declaration with ddns-updates implicitly turned on.  The notworking
one was in a shared subnet where the other subnet had ddns-updates
explicitly turned off.  My assumption was the shared subnet it was in
would remain on implicitly, which turned out to be untrue.  So, it's
either a bug or the documentation just isn't very clear.

The best thing to do is to explicitly declare ddns-updates on or off.

On Thu, Jan 7, 2010 at 2:55 AM, Simon Hobson <dhcp1 at thehobsons.co.uk> wrote:
> Jiann-Ming Su wrote:
>
>> Does the actual subnet declaration make a difference in how dynamic dns
>> behaves?
>
> It can do - as in both subnets need to have their DNS server correctly
> declared, or automatically determinable.
>
> If your DNS is all set up correctly, and you don't use signed updates, then
> the DHCP server will determine the server itself (IIRC it looks up the SOA
> record for the domain and uses the master defined there). If you use signed
> updated, or there is anything wrong with your DNS, then you need to define
> every zone that your will be updating.
>
> Looking back at your original message, I now see that you appear to be using
> 10.10.8.0/21 and 10.10.96.0/22 for your clients, and your server is at
> 172.30.8.4.
>
> Your dhcp server must know the master DNS for the zones "test.bogus"
> (assuming test.bogus is used for both subnets); and x.10.10.in-addr.arpa
> (where x is 8, 9, 10, 11, 12, 13, 14, 15, 96, 97, 98, 99) OR just
> 10.10.in-addr.arpa if you use one big zone for 10.10.x.y.
>
> It might help if you post your dhcp config file (obviously you can replace
> security keys with 'xxxx' and so on).
>
> --
> Simon Hobson
>
> Visit http://www.magpiesnestpublishing.co.uk/ for books by acclaimed
> author Gladys Hobson. Novels - poetry - short stories - ideal as
> Christmas stocking fillers. Some available as e-books.
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-- 
Jiann-Ming Su
"I have to decide between two equally frightening options.
 If I wanted to do that, I'd vote." --Duckman
"The system's broke, Hank.  The election baby has peed in
the bath water.  You got to throw 'em both out."  --Dale Gribble
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Those who count the votes decide everything.”  --Joseph Stalin



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