TCP port 123 (unknown service): NOT LISTENING. UDP port 123 (ntp service): LISTENING or FILTERED. UDP port 123 (ntp service): LISTENING or FILTERED. I am not sure if the port is available for time sync or not. But our team has confirmed that no firewall should be blocking that. It is not showing "LISTENING" because it is a UDP port?
TCP port 123 (unknown service): NOT LISTENING. UDP port 123 (ntp service): LISTENING or FILTERED. UDP port 123 (ntp service): LISTENING or FILTERED. I am not sure if the port is available for time sync or not. But our team has confirmed that no firewall should be blocking that. It is not showing "LISTENING" because it is a UDP port? Still blocking ntp ports for outbound 123? | AT&T Jan 17, 2017 Opening UDP port 123 - Cisco Community 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.
GRC | Port Authority, for Internet Port 123
Windows Time follows the NTP specification, which requires the use of UDP port 123 for all time synchronization communication. This port is reserved by Windows Time and remains reserved at all times. Whenever the computer synchronizes its clock or provides time to another computer, that communication is performed on UDP port 123. TroubleshootingNTP < Support < NTP OpenNTPD also uses high-numbered source ports so if it is able to synchronize but ntpd is not, it is very probable that the incoming UDP port 123 is blocked. If you're going to run ntpd, you need to fix your network/firewall/NAT so that ntpd can have full unrestricted access to UDP port 123 in both directions. Public NTP (Network Time Protocol) Service
Nov 26, 2009
NTP Server Test Verify that your server and NTP service are up and running. Verify that the time sources of your server are working well. Verify that your server UDP 123 port is publicly accessible. Recommended for linux server admins and linux users: How to join your linux server to the NTP pool project How to query and test an NTP server using ntpdate firewall - How to configure UFW to allow ntp to work