Merge pull request #84365 from brendan-daly-red-hat/OSDOCS-11248

OSDOCS-11248#port requirement clarification

Author: xenolinux

modules/installation-special-config-chrony.adoc

@@ -59,6 +59,11 @@ storage:
 <1> On control plane nodes, substitute `master` for `worker` in both of these locations.
 <2> Specify an octal value mode for the `mode` field in the machine config file. After creating the file and applying the changes, the `mode` is converted to a decimal value. You can check the YAML file with the command `oc get mc <mc-name> -o yaml`.
 <3> Specify any valid, reachable time source, such as the one provided by your DHCP server.
++
+[NOTE]
+====
+For all-machine to all-machine communication, the Network Time Protocol (NTP) on UDP is port `123`. If an external NTP time server is configured, you must open UDP port `123`.
+====
 ifndef::restricted[Alternately, you can specify any of the following NTP servers: `1.rhel.pool.ntp.org`, `2.rhel.pool.ntp.org`, or `3.rhel.pool.ntp.org`.]
 
 . Use Butane to generate a `MachineConfig` object file, `99-worker-chrony.yaml`, containing the configuration to be delivered to the nodes: