[plapetomain]

Optimum and Fios are two isps in the US.

> Try running a UDP-only DNS server from home on some random port.

No reason to run DNS.

However, I run openvpn udp between three houses (fios, Comcast, cablevision) for nearly 15 years. It’s pretty common, works fine.

Again in the US... cable, fiber and dsl internet service comes with a public mostly unfiltered IPv4 address, the address is dynamic but in practice it is extremely stable.

End of story.

No idea why you’re acting like such an imbecilic tool in this thread. The whole time I have mentioned that this is the case for major US “landline” ISPs. Yes there are plenty of counterexamples, not sure what point you’re trying to prove.

[3xblah]

"No reason to run DNS."

Hmmm, it was a yes or no question. Are you suggesting it work would if you did.

[plapetomain]

Yes, pretty much since most ISPs do not block UDP port 53.

I have no reason to run DNS on a home internet connection. What would a sane use case be? They don’t block it because it would be stupid to use it anyway.

Ports that are typically blocked include 67, 139, 161, 520, 547, etc.. ie dhcp, rip, smb, snmp... none of them are any great loss to those that want to run a vpn.

Running a VPN or ssh service is another story and it works fine both TCP and UDP.

[3xblah]

As someone else pointed out, the issue is mainly NAT not necessarily just "blocked" ports. What works with your ISP may not work with someone else's.