Hi I have a question on VPN using UPnP port forwarding.
Basically, I have a VPN server like OpenVPN using UDP protocol through tunnel and wanted to port forward automatically using UPnP.
I tried but turns out it won’t work. The client won’t be able to connect to the VPN server, as if there is no port opened. However manually opening the port works. So I thought both are opening port why does one work but the other don’t?
I then try to chain two routers together through LAN for the sake of testing, say the port I want to open is UDP 1195:
WAN -> Router 1 (manually open UDP 1195) -> Router 2 (UPnP UDP 1195) -> VPN Server
sort of like double-NATing? and the UPnP works!
So the question is why UPnP won’t work from WAN to Router 1? I went to some forums and read through apparently it is related to UPnP cannot do multicast through UDP. But I am still clueless as to why this happens versus manual port opening.
I hope someone here is kind enough to explain to me like I am 5 or refer me to some materials to read to better understand what is going on.
Thanks.
