How to configure the Windows 2000 Domain Name System to age records

This article discusses how to configure the Domain Name System (DNS) on a Windows 2000-based server to age records. When any records are orphaned, DNS in Microsoft Windows 2000 Server does not age these records by renaming them or by moving computers to different subnets out of their zones, unless the server is configured to perform this task.

Orphans can occur if a group of computers are installed from an image, and then renamed later on another subnet. The reverse look up pointers may not be deleted if the computer is disconnected from the network immediately after the installation. This action can cause many pointer (PTR) records in DNS which do not correctly reference a computer.

The automatic deletion of these records is possible by enabling the Aging and Scavenging feature on the DNS server.

Enable Aging and Scavenging

If you receive the error 9603 in DNS Event Viewer, enable the Aging and Scavenging feature at a server level. Optionally, set the Aging feature on zones if you need different aging periods:

1. Open the DNS manager.
2. In the left pane, under the DNS icon, right-click the server name.
3. Click Set Aging/Scavenging for all zones.
4. Click to select the Scavenge Stale Resource Records check box, and then set the interval that you want the Aging feature to use.

To set the Aging feature on an individual zone:

1. Right-click the zone, and then click Properties.
2. Click Aging.
3. Click to select the Scavenge Stale Resource Records check box, and then set the interval that you want the Aging feature to use.

Note The aging and scavenging can be performed on a per-server, per-zone, or per-record basis, according to an algorithm.

When a DNS dynamic update client registers its record for the first time, the timestamp is set from the original update, and the timestamp never updates as long as scavenging is not enabled. We recommend that you first enable Aging and Scavenging on the zone level, allowing the current clients to update their timestamp. The time period should be equal to or greater than the No-Refresh interval that is configured on the zone. As soon as this time period has passed, Aging and Scavenging can be implemented on the server level to allow scavenging on the records. Scavenging does not occur unless it is enabled at the server level and the zone level.

Additionally, you can initiate the Scavenging feature if you right-click the server name in the left pane, click Scavenge Stale Resource Records, and then click YES when you are prompted to scavenge.

You can configure the DNS server to perform scavenging automatically or manually. The StartScavenging flag also initiates Scavenging at the server.

StartScavenging is set when one or more of the following events occur:

• Dynamic update is turned on.
• The EnableScavenging flag is set from 0 to 1.
• The zone is loaded.
• The zone is resumed.

When the server is ready to scavenge records, it examines all the records in the zone one at a time. The scavenging algorithm deletes the record if the following conditions are true:

• The timestamp is not zero.
• The current time is later than the time that is specified for the record plus the following intervals:
  • The no-refresh interval.
  • The refresh interval.

To age all the records immediately, use the following dnscmd command: You may set the record to permit the record to be deleted if it is stale. If you set the record to permit the record to be deleted, you do not set the time.

Note Correct syntax is dnscmd /ageallrecords ZoneName /f. You must have scavenging enabled before running the command. Also, this command ages all records within the zone. This includes static records.

For more information, see Windows 2000 Server Resource Kit, TCP/IP Core Networking Guide, Chapter 6.