DNS issues

[plexer]

I've run netdiag on both my DC and all looks ok.

However I still seem to get machines resolving wrongly.

Today I pinged a laptop T1-15 which was not connected to the network as I was trying to sort the wireless out.

Yet it responded as the ip address dns said that this laptop has is in use by another pc.

Ben

[rvdmast]

sounds like your DHCP and DNS server(s) are "out of sync", possibly due to
aging and scavenging being configured incorrect.
Check this kb article:
How DNS dynamic updates work together with the DNS "aging and scavenging" process in Windows 2000 and in Windows Server 2003

[plexer]

Had a quick scan of that article what the best practice to set dhcp and dns to then?

Ben

[theboyhope]

Well, ideally you wouldn't need scavenging but removal of records just doesn't work as well as the registration.

I take it your lease duration is 8 days and your refresh and no-refresh are 7?

[theboyhope]

PS - it could be WINS if you're still using that.

[plexer]

no wins.

Lease is 5 days.
Enable DNS dynamic updates according to the settings below is checked
Always dynamically update dns a and ptr records is now checked other option was checked before.
Discard a and ptr records when lease is deleted is checked
dynamically update dns a and ptr records for dhcp client that do not request updates is checked.

Ben

[theboyhope]

I take it you have you checked for and confirmed the presence of duplicate records in DNS already?

If so, have you now enabled scavening?

[rvdmast]

I believe the rule of thumb was that the sum of the DNS refresh- and no-refresh interval should equal the DHCP lease duration.

[theboyhope]

I can't make much sense of that rule myself. Could you go into why it should be set that way?

The MS default settings put the refresh and no-refresh intervals at 87.5% of the DHCP lease duration which makes a lot of sense. The DNS server isn't pestered with unnecessary traffic for the majorify of the duration of the lease.

[plexer]

Scavenging is enabled and always has been I'm not quite sure what the interval for that should be.

Ben