TTL when updating via DDNS

[Glenn Satchell]

>Date: Wed, 09 Jul 2008 11:31:41 +0200
>From: Marc Muehlfeld <Marc.Muehlfeld at medizinische-genetik.de>
>To: dhcp-users at isc.org
>Subject: TTL when updating via DDNS
>
>Hello,
>
>I'm using dhcpd 3.0.6 that came with openSUE 10.3. I setup DDNS for my 
>clients, but I saw, that the entries created in named have a short TTL. After 
>some searching on the web, I found out that the entries are allways created 
>with half "default-lease-time", which I can confirm.
>
>But I have the problem, that clients that run 24x7 disapper from DNS after TTL 
>and are not accessible through the FQDN any more. I found an option "ddns-ttl" 
>  on different pages of the internet. When I set this parameter, it doesn't 
>make dhcpd complain. But it doesn't work, either.
>
>How can I ensure, that the entries stay in the zone files until the client 
>release or renew it's lease?
>
>Regards
>Marc

The TTL has nothing todo with deleting an entry from a zone file. TTL
is how long a dns server will *cache* that hostname/IP pair after it
has done a lookup. If you think about it, most clients renew at half
the default lease time, so making this the TTL makes sense.

If you have hosts being deleted from the zone file then you have a
different problem. Are your clients successfully renewing their leases?
Are there any log messages indicating that dhcpd asked for the zone
entry to be deleted? Is there anything related to this inthe (I assume)
bind  logs?

Can you please post your dhcpd config file (or a reasonable example if
it is huge).

regards,
-glenn