Scavenging – Automatic purge outdated DNS Resource Records added dynamically

Windows DHCP can register host records (A) and Reverse lookup or Pointer (PTR) resource records automatically whenever you add a new device to the network. This enables simplified and easy network administration. However, these records are not automatically purged when they are stale or outdated (say when the host gets a new IP address) and they remain in the DNS zone database indefinitely. This can cause network issues and can prevent host names from re-used.

However, this can be overcome by configuging the DNS Server to track the age of each dynamically-assigned record and to periodically remove records (also called scavenging) that are older than the number of days that you specify.

The age of a resource record is based on when it was created or when it was last updated. By default, Windows client systems by default send a request every 24 hours to the DNS server to update their records. This prevents the records the records from being removed from the database.

 

In Windows Server 2008, Scavenging is disabled by default. To enable and configure on Windowss 2008 DNS Server, please do the following:

1. Click Start, point to Administrative Tools, and then click DNS. This starts the DNS Server MMC snap-in.

2. In the console tree, click the applicable DNS server.

3. On the Action menu, click Properties.

4. Click the Advanced tab, select “Enable automatic scavenging of stale records” and click OK.

5. On the Action menu, click Set Aging/Scavenging for All Zones.

6. Click “Scavenge stale resource records” check box, and then click OK. Default is “7 days”

7. In the Server Aging/Scavenging Confirmation dialog box, select “Apply these settings to the existing Active Directory-integrated zones” and click OK.

This should enable scavenging stale Host and pointer records in Windows 2008 DNS server.

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