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This chapter is from the book

Updating Client DNS Information with DHCP Servers

The workstation platform determines how the client interacts with the DHCP and DNS servers. Recall from earlier in the book that Windows 2000 clients can send update requests directly to a DNS server to update its own pointer and address records, known as a dynamic update . Alternatively, the client can request that the DHCP server make the update on its behalf.

Using an additional DHCP option included in the DHCPRequest message, the Client FQDN option (option 81), and the client's fully qualified domain name (FQDN), a Windows 2000 DHCP client can pass its FQDN to the DHCP server and inform the server how to perform the update. The client can either perform the update or inform the DHCP server (using option 81 included with the DHCPRequest message) that it should perform the update on its behalf.

Clients running platforms earlier than Windows 2000 do not support dynamic updates and are unable to interact directly with a DNS server like a Windows 2000 client can. When a pre-Windows 2000 client (or a non-Microsoft client) receives an IP address from a DHCP server, the DHCP server can be configured to perform the updates on behalf of these clients. As you just saw, Windows 2000 clients can have this functionality configured as well, but the difference here lies in the fact that non-Windows 2000 clients cannot update their records with the DNS server themselves, as do Windows 2000 clients.

Note

Be sure you know which clients support dynamic DNS and understand how to configure DHCP for those clients that cannot update their own records.

Configuring DHCP/DNS Integration

To configure DHCP for DNS integration, right-click the DHCP server within the management console and choose Properties. If you select the DNS tab, you'll see a dialog box similar to the one shown in Figure 3.9. Three settings can be configured for DNS integration, which are described as follows:

  • Automatically update DHCP client information in DNS — This option is selected by default. The DHCP server will register host records and pointer records when requested to do so by the client. In an environment that runs only Windows 2000, the default setting is sufficient because Windows 2000 clients are capable of updating their own records directly with the DNS server. Two suboptions are listed. The Update DNS only if DHCP client requests option is selected by default. If you have pre-Windows 2000 DHCP clients on the network, select the option to always update DNS.

  • Discard forward (name-to-address) lookups when lease expires — This option is enabled by default as well. Once the IP address lease expires (the client is no longer using it), the DHCP server sends a request to the DNS server that the DNS record for the client should be discarded.

  • Enable updates for DNS clients that do not support dynamic updates — If you have pre-Windows 2000 or non-Microsoft clients on the network, select this option to have the DHCP server perform DNS updates on behalf of the clients.

03fig09.jpgFigure 3.9. Configuring DHCP integration with DNS.

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