Originally Posted by lincolnjkc

There are a variety of VPN technologies so it's not possible to say universally "VPN will work"

E.g. My company uses Cisco solutions and the AnyConnect SSL VPN client which essentially passes traffic the same way as HTTPS webpages get transferred (with UDP if available for increased performance) which means most firewalls that pass "normal" web traffic are also happy with to pass the VPN traffic.

I have clients that use dozens of variations (Cisco IPSec, Palo Alto Networks Global Protect, a slightly different flavor of Global Protect, ZScaler, a different implementation of ZScaler, ... ) some similarly use TCP port 443, some use different ports, so that's the client side.

On the aircraft side some of the providers block almost everything that's not HTTP or HTTPS, some allow more traffic, some that allow HTTP/HTTPS won't work because they futz with packets in odd ways.