Enabling Dynamic DNS Updates by a DHCP Server

DNS provides name-to-address and address-to-name services for the Internet. Once a DNS mapping is made, a system can be reached through its host name or its IP address. The system is also reachable from outside its domain.

The DHCP service can use DNS in two ways:

• The DHCP server can look up the host name that is mapped to an IP address that the server is assigning to the client. The server then returns the client's host name along with the client's other configuration information.

• The DHCP server can attempt to make a DNS mapping on a client's behalf, if the DHCP server is configured to update DNS. The client can supply its own host name when requesting DHCP service. If configured to make DNS updates, the DHCP server attempts to update DNS with the client's suggested host name. If the DNS update is successful, the DHCP server returns the requested host name to the client. If the DNS update is not successful, the DHCP server returns a different host name to the client.

You can enable the DHCP service to update the DNS service for DHCP clients that supply their own host names. For the DNS update feature to work, the DNS server, the DHCP server, and the DHCP client must be set up correctly. In addition, the requested host name must not be in use by another system in the domain.

The DHCP server's DNS update feature works if the following statements are true:

• The DNS server supports RFC 2136.

• The DNS software is based on BIND v8.2.2, patch level 5 or later, whether on the DHCP server system or the DNS server system.

• The DNS server is configured to accept dynamic DNS updates from the DHCP server.

• The DHCP server is configured to make dynamic DNS updates.

• DNS support is configured for the DHCP client's network on the DHCP server.

• The DHCP client is configured to supply a requested host name in its DHCP request message.

• The requested host name corresponds to a DHCP-owned address. The host name could also have no corresponding address.