Forward traffic from IP6 to IP4

PeterMmm asked:

On my debian6 server is a process that only listen on IPv6 but I also need to listen on IPv4. It seems the program is IPv6 only. Is there a way to route the traffic fom IPv6 to IPv4 on the same host ?

My answer:

This happens automatically when IPv4-mapped IPv6 is in use.

Check the sysctl net.ipv6.bindv6only; if it is set to 0, then IPv4-mapped IPv6 is in use, and incoming IPv4 connections will be mapped and sent to the IPv6 listener.

However, individual processes can override this behavior so it’s not a cure-all. If you want a specific answer for your circumstance, you’ll have to name the program.

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