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armani
Asked: 2014-01-10 08:53:47 +0800 CST

DNS A records disappear, but PTR records still remain

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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?

domain-name-system

1 Answers

  1. Best Answer

    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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