Dynamic updates

Last Updated: 2021-08-31

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 8 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 System i®
model, different System i models, or other systems that are capable of
dynamic updates.