Routers simply need to block incoming unestablished packets (all modern routers allow for this) to replicate NAT security without NAT translation. Then you just punch holes through on IP addresses and ports you want to run services on and be done with it.
Now, some home routers aren’t doing this by default, but they absolutely should be. That’s just router software designers being bad, not IPv6’s fault, and would get ironed out pretty quick if there was mass adoption and IPv4 became the secondary system.
To be clear, this is not a reason not to be adopting IPv6.
Routers simply need to block incoming unestablished packets (all modern routers allow for this) to replicate NAT security without NAT translation. Then you just punch holes through on IP addresses and ports you want to run services on and be done with it.
Now, some home routers aren’t doing this by default, but they absolutely should be. That’s just router software designers being bad, not IPv6’s fault, and would get ironed out pretty quick if there was mass adoption and IPv4 became the secondary system.
To be clear, this is not a reason not to be adopting IPv6.
This is called a firewall