[Samba] Internal DNS - TTL enforcement for dynamic updates

Kai Blin kai at samba.org
Thu Nov 1 02:07:42 MDT 2012

Hash: SHA1

On 2012-10-31 22:25, Dmitry Khromov wrote:

> Samba 4 rc 3. I had noticed a strange behavior. If host creates a 
> record, it won't be further updated until the record gets deleted 
> manually. What could cause this?

What updates are you expecting?

> Another question: how could the dynamically added record's TTL be 
> enforced? For example, we have a user-based VLAN assignment in our 
> networks. When Windows host boots, it authenticates with machine 
> account and goes to the one of "parking" VLANs. Later, when user
> logs in, he gets a different VLAN and different IP address. So, we
> really want other DNS servers to not cache this records for too
> long. Normally, this is done by modifying SOA record (and, as I
> recall, Samba's internal DNS respects TTLs in SOA). But samba-tool
> can't edit SOA records, MMC DNS snap-in fails to do it too.

The TTL only affects caching decisions on the resolver side, so the
internal DNS actually doesn't do anything with the TTLs apart from
serving them out with the record.

Now, if your clients register their DNS records, they get to pick the
TTL of the entry themselves. This can probably be affected with a GPO
somehow, but I don't know the AD stuff enough to know where to look.

I don't think the TTL of the SOA record should affect anything apart
from how long resolvers cache the SOA record.

- -- 
Kai Blin
Worldforge developer http://www.worldforge.org/
Wine developer http://wiki.winehq.org/KaiBlin
Samba team member http://www.samba.org/samba/team/
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