My home router seems to be blocking UDP 123.
sudo ntpdate -u time.apple.com
works as expected, but
sudo ntpdate time.apple.com
I get: "no server suitable for synchronization found"
I can get a root shell on my router (yay!) and it seems to be running ntp, so maybe that's it? But killing ntp on the router does not help, any iptables stuff I can think/find to set does not help, and setting DMZ to my laptop I can ssh from outside, but when I
sudo nc -u -l 123
I can't get a packet in from outside to that.
Direct DNS queries work, and as mentioned higher-port-number NTP works, so UDP in general is fine.
Why might this be happening? Any way I can debug or fix it, short of swapping the firmware or getting a new router?