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DNS Scavenging

First it is important to note that the dns record is owned by the node or individual computer. The dns record is not owned by the dns server. The dns server only keeps a record of the individual dns records. Kinda strange, right?

What often happens is that the dns record changes on the individual computer but the dns server is not updated. When a query is run against the dns server, the record is incorrect because it was not updated.

Secondly, there are 2 server roles here that work together; DNS and DHCP.

Thirdly, the lease-time should be set to double the refresh-rate.

Let's begin by starting with the DNS server:

  • -right-click on the server-name.
  • -checkmark "Scavenge stale resource records".
  • -set both the no-refresh and the refresh interval to: 2-days
  • -click OK
  • -click "Apply these settings to existing..."
  • -click OK

Great! You are on your way!

Let's move to the the DHCP server:

  • -right-click on each dhcp zone.
  • -click PROPERTIES.
  • -set the dhcp-lease-time to: 4 days
  • -click the DNS tab (at the top).
  • -checkmark "Enable DNS Dynamic Updates..."
  • -bullet "Always Dynamically Update DNS"
  • -checkmark "Discard A and PTR records..."
  • -checkmark "Dynamically Update DNS Records..."

Awesome! Almost finished. Now the second part on the DHCP server. This will allow the DHCP server to update the DNS server:

  • -right-click on IPV4.
  • -click PROPERTIES.
  • -click ADVANCED tab (at the top).
  • -click CREDENTIALS button
  • -type in a USERNAME/DOMAIN/PASSWORD for an administrator account that can update DNS.

Finally, let's move back the DNS server:

  • -right-click on the server-name.
  • -click ADVANCED tab (at the top).
  • -checkmark "Enabled Automatic Scavanging of Stale Records"
  • -set the scavenging interval to: 1-day.

You're done!


If you have more than one DHCP server (for example, mulitple locations):

  • -open AD Users-&-Computers
  • -find the built-in group, DnsUpdateProxy
  • -add the DHCP servers from all locations.

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