IPv4 connectivity to IPv6-only host

Solution 1:

It depends on the protocol, and you didn't provide much details. Usually something like haproxy will work. There is good documentation for the opposite situation (making content on an IPv4-only server available over IPv6) on the ISOC Deploy360 website that you can use as a starting point. Just reverse the IP addresses.

A simple example based on that documentation:

global
    user haproxy
    group haproxy
    daemon
    log /dev/log daemon

defaults
    timeout client 5000
    timeout connect 5000
    timeout server 10000

listen webserver1
    bind 192.0.2.1:80
    mode tcp
    server webserver1 2001:db8:abc:123::cafe:80

The IPv4 address is the address of your dual-stack server and the IPv6 address is the address of the IPv6-only server.