The protocol you're looking for is PCP which is the NAT-PMP successor that also works with IPv6: https://en.wikipedia.org/wiki/Port_Control_Protocol https://en.

The protocol you're looking for is PCP which is the NAT-PMP successor that also works with IPv6: https://en.wikipedia.org/wiki/Port_Control_Protocol https://en.wikipedia.org/wiki/Port_Control_Protocol Unfortunately it's going to take a while until it's widely supported.