Dynamic updates

You can configure a Dynamic Host Configuration Protocol (DHCP) server to work with a Domain Name System (DNS) server to dynamically update the client information in the DNS when DHCP assigns the client an IP address.

DNS is a distributed database system for managing host names and their associated IP addresses. With DNS, users can locate hosts using simple names, such as www.example.com, rather than using the IP address (xxx.xxx.xxx.xxx).

In the past, all DNS data was stored in static databases. All DNS resource records had to be created and maintained by the administrator. Now, DNS servers running BIND 9 can be configured to accept requests from other sources to update zone data dynamically.

You can configure your DHCP server to send update requests to the DNS server each time it assigns a new address to a host. This automated process reduces DNS server administration in rapidly growing or changing TCP/IP networks, and in networks where hosts change locations frequently. When a client using DHCP receives an IP address, that data is immediately sent to the DNS server. Using this method, DNS can continue to successfully resolve queries for hosts, even when their IP addresses change.

You can configure DHCP to update address mapping (A) records, reverse-lookup pointer (PTR) records, or both on behalf of a client. The A record maps the client's DNS name to its IP address. The PTR record maps a host's IP address to its host name. When a client's address changes, DHCP can automatically send an update to the DNS server so that other hosts in the network can locate the client through DNS queries at its new IP address. For each record that is updated dynamically, an associated text (TXT) record is written to identify that the record was written by DHCP.

Note: If you set DHCP to update only PTR records, you must configure DNS to allow updates from clients so that each client can update its A record.

Dynamic zones are secured by creating a list of authorized sources that are allowed to send updates. DNS verifies that incoming request packets are coming from an authorized source before updating the resource records.

Dynamic updates can be performed between DNS and DHCP on a single IBM® i model, different IBM i models, or other systems that are capable of dynamic updates.