Dec 18, 2016

UDP port 123 is the default NTP port. So check your NTP configuration. The most probably it's standard synchronization. You'd have to capture packets with tcpdump and inspect the content (wireshark). Solved: Different between port 123 (ntp) and 37 (timeserve Port 37 has been obsolete for a very long time and is one of the many archaic ports that should be disabled. NTP does not use 37 at all, only port 123. I would disable the following services in inetd.conf immediately, even if the security team has not reported them: daytime time echo discard chargen ntalk uucp help with connecting to NIST NTP server on port 123

How to allow timesync over UDP port 123 (SNTP) and TCP

networking - How to check if port 123 is ready for time 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?

How to enable and configure NTP on a SonicWall UTM

The NTP server requires that port 123 to be open. As I said, I never had any problem configuring this with my previous routers (used for a long time or just a few days), R7000, R8500, AC87U and AC8500.