Why does NTP require bi-directional firewall access to UDP port …
Jun 2, 2014 · NTP requires bi-directional access on port 123 because the NTP RFC specifies the following regarding the source port of the client: When operating in symmetric modes (1 and …
firewall - Why open 123/udp in both directions? - Super User
Jun 22, 2022 · When using an NTP server in an environment with a firewall, it is common to open 123/udp in both directions. So my question is, why is it necessary to open it in both directions?
What are the iptables rules to permit ntp? - Super User
May 16, 2010 · My server's clock is wrong because the firewall doesn't permit ntp traffic. What are the iptables rules required to allow the ntp client to get out and back? Any suggestions how to …
Change source port of NTP requests on router using iptables
Feb 20, 2017 · Using source NAT to rewrite the source port number from 123 would not change the fact that you're still connecting to remote NTP servers that listen on destination port 123. …
Why can't I connect to any NTP server from Windows?
Feb 7, 2024 · NTP has two modes: client-server mode and symmetric mode. Somewhat unusually they're distinguished by UDP ports: client-server uses the typical model where the source port …
Allowing Outbound UDP 123 - Security Implications? - Super User
Sep 30, 2015 · What are the risks of allowing outbound UDP 123 for an internal server (archive server) to synchronize with the external NTP server. Our internal server always displays …
windows - NTP server, port not open - Super User
Jun 11, 2021 · By default, nmap tests TCP ports. The NTP protocol uses only UDP, and the ntpd service only sets up UDP sockets, not TCP. Those do not interact in any way – probing the …
NTP sync fails but NTP servers are reachable on Windows 10
Apr 2, 2024 · Linux NTP software usually adheres to the protocol specifications and uses an ephemeral source port in client/server mode, like most other UDP software would (the …
Windows w32tm not answering NTP requests - Super User
Jul 4, 2023 · I'm trying to setup an NTP server on my Windows machine. I'll give you a quick overview of the architecture I'm aiming for: The setup is as follows: on the Windows computer …
ntp - How to use ntpdate behind a proxy? - Super User
Jul 6, 2011 · Is it possible to use ntpdate behind an HTTP proxy with authentication? In case it is not possible, are there any good alternatives?