Jun 9, 2020

Using nsupdate to make dynamic DNS changes

The command, nsupdate is used to perform dynamic DNS updates from the CLI.

Before the dynamic update:

jemurray@linux-host:~ $ host dyntest.jason.example.com
Host dyntest.jason.example.com not found: 3(NXDOMAIN)

Running the dynamic update command:

jemurray@linux-host:~$ nsupdate
> server 192.168.0.1
> update add dyntest.jason.example.com 86400 A 127.0.0.1
> send

If the dynamic updates fails, verify there are no ACL’s prohibiting dynamic updates:

May 11 08:14:20 192.168.0.1 named[31289]: client 192.168.3.4#61452: update 'jason.example.com/IN' denied

The allow-update line is used to control which IP addresses are allowed to send dynamic updates:

zone "jason.example.com" in { # jason.example.com
  type master;
  database infoblox_zdb;
  masterfile-format raw;
  file "azd/db.jason.example.com._default";
  allow-update { key DHCP_UPDATER_default; 172.16.0.0/12; 10.0.0.0/8; };
  notify yes;
 };

Validate the change executed properly:

jemurray@linux-host:~$ host dyntest.jason.example.com
dyntest.jason.example has address 127.0.0.1