Opening UDP port 123 - Cisco Community
How to test if my home router is blocking NTP port 123 Jun 04, 2002 List of TCP and UDP port numbers - Wikipedia 248 rows How To Configure NTP Server in Windows Server 2019 Open up Registry Editor. Click on the start icon in your Server and search for “Run” application. From … Windows Server: Test an NTP Time Server | Basics for
Re: Opening UDP port 123 NTP should be able to go out across your firewall just like HTTP requests do. Can you crank up NTP logging to make certain that those servers *ever* respond, as some publically listed NTP servers are dormant.
Windows Server: Test an NTP Time Server | Basics for Sep 25, 2018 Troubleshoot Network Time Protocol (NTP) - Cisco
firewall - How to configure UFW to allow ntp to work
RFC 958 - Network Time Protocol (NTP)