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>IPv4 servers are reachable by IPv6-only clients How does this work?

• zinekeller 4y ago
  It unfortunately involves CGNATted IPv4, but it's either DS-Lite (https://datatracker.ietf.org/doc/html/rfc6333 https://datatracker.ietf.org/doc/html/rfc6333) where the end-user router emulates a dual-stack network but encapsulates IPv4 traffic on IPv6 from the perimeter to the CGNAT device at the ISP or just plain NAT64/DNS64 (https://datatracker.ietf.org/doc/html/rfc6147 https://datatracker.ietf.org/doc/html/rfc6147) where IPv4 traffic is relayed at dedicated IPv6 addresses operated by the ISP with the help of special DNS (which might be the GP meant for IPv6-only networks, but it tends to be unreliable for a lot of reasons). In practice DNS64 is now being removed from a majority of networks because some specialty applications (I say "specialty" but these are work VPNs, conference systems and the like) reacts badly (because usually they can't understand IPv6 in the first place), replaced by either DS-Lite or plain dual-stack (possibly with CGNAT for IPv4).
• hotpotamus 4y ago
  I forget this part of IPv6 class (I've literally gone to several IPv6 classes throughout the years but then end up forgetting details because I've yet to use it in production), but since the IPv6 space is so large, it's trivial to put an IPv4 address into it, and so they make NAT 6to4 type gateways that map the IPv4 internet into a block on the IPv6 network.
  • ignoramous 4y ago
    This wikipedia entry is a pretty handy reference: https://en.wikipedia.org/wiki/IPv6_transition_mechanism https://en.wikipedia.org/wiki/IPv6_transition_mechanism