2022年6月22日 · (Linux PCs being able to use NTP, but Windows PCs mysteriously not receiving any replies, and it always turned out to be a port-123 firewall rule.) Dynamically assigned ports are usually chosen from the "ephemeral" range, so they generally don't collide with any service worth blocking (as service ports are typically chosen from a lower range).

2014年6月2日 · When operating in symmetric modes (1 and 2), this field must contain the NTP port number PORT (123) assigned by the IANA. Since the client's source port is 123, when the server sends the response back it'll send it to port 123. Naturally, in order to be able to receive that response the client must allow incoming responses on port 123.

2009年6月10日 · Confirm UDP port 123 is open throughout the network for NTP packets. Alternate design option . If you have a high end router, use it as a "NTP master" and have it poll to public time servers, and everyone else poll this high end router.

2017年2月20日 · iptables -t nat -I POSTROUTING -p udp -m udp --sport 123 -j MASQUERADE --to-ports 60000-61000. AT&T blocks outbound UDP traffic with source port 123, to mitigate common NTP reflection attacks from compromised machines on customer networks. Destination port 123 is allowed, but most NTP clients use 123 for the source port as well.

2010年5月16日 · in any case, NTP is UDP port 123, so, assuming you are a CLIENT and want to access NTP servers you'd do: iptables -A OUTPUT -p udp --dport 123 -j ACCEPT iptables -A INPUT -p udp --sport 123 -j ACCEPT these will append the rules to the end of your OUTPUT and INPUT chains. Assuming you want to be a server, you'd do

2024年4月2日 · Opening port 123 in the router firewall; Changing DNS settings (I use DNS-over-TLS) and have not gotten it to work. My router is on a double NAT configuration (i.e. Internet - Another router I don't control - My router - My PC), which can cause NTP problems, but then I don't understand how my Linux laptop can sync. Edit 1: NTP packet with response

Our Switch (3750 & nexus 5000 & nexus 7000) be scan with udp 123 and 161 port open on management interface. I know it's open for NTP and SNMP.

2004年7月6日 · Good morning, I've been having problems with external NTP time servers not responding, causing time sync problems in our network. Can someone tell me the best way to handle allowing traffic on UDP port 123?

2024年10月9日 · You can set up OpenVPN on any UDP port number you like, it doesn't care; but. it might break Synology's own NTP access, depending on which NTP software it uses, because an often-used NTP "symmetric" mode actually uses ports '123→123' instead of the typical 'random→123' (Windows NTP client is one example but I've seen this on Linux as well).

2015年9月30日 · 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 incorrect time intervals because it is currently synchronized with our internal NTP server.