For about a week my server (SBS 2003 Standard SP2) is unable to synchronize with an internet time server. Event log shows time server is unreachable. Windows Firewall is set to open UDP port 123 but an external port scanner reports UDP 123 is not reachable. The server is connected to the internet via a Netgear WPN824v3 router. Port forwarding is set by UPNP. The router shows UDP 123 is forwarded to my server. I even tried making my server a DMZ, with no luck.
The problem seems to have started when I turned off UPNP and configured my router's port forwarding manually to enable VPN. In manual mode, I was unable to forward port 123 as the router (wrongly) complained it conflicted with an existing rule. I did a factory reset of the router (hard reset with the reset button) and reconfigured with UPNP. Everything looks fine, but port 123 is still unreachable.
I tried various methods outlined here to force synchronization, but they fail with message that source is unreachable. I turned on Windows Firewall logging (in Group Policy) to report dropped packets, but so far there is no report.
I suspect it is a firewall or router issue, but I certainly can't find it.
An help would be greatly apreciated!