Reference:
Port 123 is what needs to be opened to ensure all devices receive the time from the local environment with the least administrative effort in a private cloud model. Port 123 is the port used by NTP (Network Time Protocol), which is a protocol that synchronizes the clocks of network devices and systems. NTP can help to ensure accurate and consistent time across different devices and systems in a cloud environment, which can facilitate coordination, communication, logging, auditing, etc.