Our epic treatise on how NAT traversal works (in general, not specific to Tailscale) mentions this. IPv6 greatly reduces the amount of pain for p2p connections,

Our epic treatise on how NAT traversal works (in general, not specific to Tailscale) mentions this. IPv6 greatly reduces the amount of pain for p2p connections, but does not eliminate some of the fundamentals (stateful firewall traversal) if you want it to be zero-config: https://tailscale.com/blog/how-nat-traversal-works/ https://tailscale.com/blog/how-nat-traversal-works/ But until deployment hits 100%, and until ISPs start caring about IPv6 reliability the way they do about IPv4, "just use IPv6" can't be your answer. It's lovely when it works, but you need to do something other than "give up" when it doesn't. (also, as long as the internet is dual-stacked, doing IPv6 right also implies figuring out if NAT64 is in play, and wielding it correctly; so arguably IPv6 adds more complexity to the overall story, for now :) )