Integrating DNS with DHCP

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Applies To: Windows Server 2003, Windows Server 2003 R2, Windows Server 2003 with SP1, Windows Server 2003 with SP2

Windows Server 2003 DNS supports DHCP by means of the dynamic update of DNS zones. By integrating DHCP and DNS in a DNS deployment, you can provide your network resources with dynamic addressing information stored in DNS. To enable this integration, you can use the Windows Server 2003 DHCP service.

The dynamic update standard, specified in RFC 2136: Dynamic Updates in the Domain Name System (DNS UPDATE), automatically updates DNS records. Both Windows Server 2003 and Windows 2000 support dynamic update, and both clients and DHCP servers can send dynamic updates when their IP addresses change.

Dynamic update enables a DHCP server to register address (A) and pointer (PTR) resource records on behalf of a DHCP client by using DHCP Client FQDN option 81. Option 81 enables the DHCP client to provide its FQDN to the DHCP server. The DHCP client also provides instructions to the DHCP server describing how to process DNS dynamic updates on behalf of the DHCP client.

The DHCP server can dynamically update DNS A and PTR records on behalf of DHCP clients that are not capable of sending option 81 to the DHCP server. You can also configure the DHCP server to discard client A and PTR records when the DHCP client lease is deleted. This reduces the time needed to manage these records manually and provides support for DHCP clients that cannot perform dynamic updates. In addition, dynamic update simplifies the setup of Active Directory by enabling domain controllers to dynamically register SRV resource records.

If the DHCP server is configured to perform DNS dynamic updates, it performs one of the following actions:

  • The DHCP server updates resource records at the request of the client. The client requests the DHCP server to update the DNS PTR record on behalf of the client, and the client registers A.

  • The DHCP server updates DNS A and PTR records regardless of whether the client requests this action or not.

By itself, dynamic update is not secure because any client can modify DNS records. To secure dynamic updates, you can use the secure dynamic update feature provided in Windows Server 2003. To delete outdated records, you can use the DNS server aging and scavenging feature.