Hello,
I wonder what TCP ports are to be left open in a firewall to let the tunnel work.
Regards
JPPO
dont need to allow any ports..just protocol 41 and imho, ping
IPv4: Protocol 41 from/to the tunnel server's IPv4 address.
IPv6: ICMP6 echo-request and reply from/to the tunnel server's IPv6 address ending ::1 ("Server IPv6 Address Tunnel Endpoint") and your host's IPv6 address ending ::2 ("Client IPv6 Address Tunnel Endpoint").
To do anything useful, obviously your IPv6 routed address(es) must also be opened somehow. That's up to you.