We've been having issues with DNS records dropping. Usually it is from DHCP reservations, like printers. Yesterday it was two of our main servers, also DHCP-reserved. Right now I'm looking at a normal DHCP (non-reserved) computer that is not able to be ping'd by name or nslookup'd because the A records doesn't exist, but "ping -a IP_Addr" resolves the name successfully because the PTR record exists in the Reverse Lookup Zone. Records on both DNS servers match.

These are Windows DNS servers, by the way. Primary I think is 2003, and Secondary is for sure 2008 R2.

Scavenging Period: 4 days on primary DNS server, disabled on secondary

No-Refresh Interval: 12 hours in Forward Lookup Zone, 1 day in Reverse Lookup Zone, on both servers

Refresh Interval: 7 days for both Forward and Reverse, for both servers

DHCP Lease Time: 2 days for most subnets (including PC currently experiencing the issue), 1 day for servers (like the ones suffering the issue yesterday)

My fix yesterday was to add the A record manually. Since they now show up as static entries with no timestamp, I assume they'll never get scavenged (further assuming scavenging is my issue?), but as you can see this is happening more and more on my network, I need to figure out what's causing these DNS records to get lost.

Any pointers? I'm not going to add the A record to this problem PC right now so I can perform troubleshooting steps to figure this out, if need be.

EDIT: Last night some time, the A record came back for that PC, so I can't troubleshoot it in particular. But the underlying issue exists, and I'm afraid of the call where servers or printers randomly stop working for my users. What's going on?

  • Have you checked the Event logs on the DHCP server (as this will be registering the A records) and the DNS server to see if anything comes up? – Sam Jan 10 '14 at 17:26
  • I'm having a tough time finding where that is in the logs. The DHCP server is also the primary DNS server, by the way. – armani Jan 10 '14 at 19:17
  • I think I'd have a tough time finding the right entry as well. I would probably wait until it next occurs then check the DHCP lease for the time it was issued then check all logs at that time for anything that looks like it could be related to the DNS not registering. – Sam Jan 11 '14 at 6:54

Create an AD account, member of "Domain Users", set "Password never expires", in advanced DHCP properties click "Credentials..." and enter that user there. Then make the following setting in DHCP

[x] Enable DNS dynamic updates according to the settings below

[ ] Dynamically update DNS A and PTR records only if requested by the DHCP clients

[x] Always dynamically updates DNS A and PTR records

[x] Discard A and PTR records when lease is deleted

[x] Dynamically update DNS A and PTR records for DHCP clients that do not request updates (for example, clients running Windows NT 4.0)

This will make DHCP the owner of the DNS entries and allow it to delete the PTRs as well. Settings as per TechNet best practice.

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  • Cool. A link to the TechNet resource would be neat, but this looks really useful as it is. – Felix Frank Nov 21 '14 at 15:47
  • I'll try to find it again. I usually just copy these things into notepad files, one file per fix per problem. Helps reduce clutter. – eckinator Dec 2 '14 at 23:05

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