In situations where IPv6 connectivity performs better than IPv4, you might want to force SSH to use IPv6. In interactive mode this can be achieved with the -6 commandline parameter.
But in situations where you can't modify the commandline parameters a different approach is needed (for example in rsync backup scripts which use SSH as underlying transport layer).

We can use the ssh_config file to encforce that IPv6 is used for a specific host:

Host myipv6host
	AddressFamily inet6

This instructs all SSH commands to use IPv6 when connecting to myipv6host.

The same approach also works to force usage of Legacy IP by specyfing inet as address family.