The Dynamic DNS (DDNS) feature of Novell DNS/DHCP Services provides a way to update DNS with accurate A records and Pointer records for address assignments made by a DHCP server. These resource records are required so that both name-to-address and address-to-name DNS resolutions can be made. DDNS eliminates the need for further error-prone configuration of DNS for each host address change.
DDNS is enabled by configuring a subnet address range with Always Update parameter set to on. You must also specify a zone reference in the Subnet object so that the DHCP server can determine which zone to update.
When DDNS is active, the DHCP server updates the DDNS server for the zone, adding or deleting the corresponding Address and Pointer records. The DHCP server also notifies the DDNS server when leases expire, causing the A and PTR records to be deleted. If a lease is renewed, no action occurs because none is necessary.
Only subnet address ranges that are Dynamic DHCP or Dynamic BOOTP and DHCP can use the Dynamic DNS update feature. For a DDNS update to occur, Always Update must be specified for the range's DNS update option and a DNS zone must be specified to link the Zone object to the subnet. When these conditions are met, the DHCP server initiates a dynamic DNS update when an address is assigned to a client.
When a client that is subject to DDNS updates is granted a lease by the DHCP server, the server updates its database and NDS to store the transaction. The DHCP server also contacts the DNS server and submits a request for a DNS update.
For DDNS updates, the DNS server requires the fully qualified domain name (FQDN) and the IP address of the client. The DHCP server knows the IP address, but it must assemble the FQDN from the hostname and the subnet's domain name.
The DNS server usually maintains two resource records for each client. One maps FQDNs to IP addresses using A records. The other maps the IP address to the FQDN using PTR records. When DDNS is enabled and a client receives an address from the DHCP server, the DNS server updates both of these records.
When a client loses or ends its lease and is subject to DDNS updates, the DNS server receives the DDNS update request and deletes the PTR and A records associated with the client.