My situation is the following, I have a website hosted on a linux machine(with apache2), unfortunately my router (unitymedia) provides only a port filtering for the IPv6 adresses, but no port forwarding for IPv4. Then I have created a noip account, I have created a domain name and installed a duc on my machine. Noip has given a kind of virtual IPv4 number to my machine so I thought it would work, unfortunately the connections from IPv6 works but the IPv4 connections that are not local return a timeout error. (IPv4 connections on the local network work).
I think there are two possibilities, the box is cutting the IPv4 connection or the website is replying with IPv6 on the virtual IPv4 connection (is that possible ?).
Is there a way to get around this trouble ? (I cannot change the box/router).
edit:
if I try to use socat I obtain the following error :
sudo socat TCP4-LISTEN:22,fork,su=nobody TCP6:[2a02:xxxx:xxx:xxxx:xxxx:xxxx:xxxx:xxx]:22
socat[10594] E bind(5, {AF=2 0.0.0.0:22}, 16): Address already in use