To be precise, the prefixes advertised within an RA message have an 'autoconfig' flag; if you unset this flag then hosts won't do SLAAC. So if you set the M-fl

To be precise, the prefixes advertised within an RA message have an 'autoconfig' flag; if you unset this flag then hosts won't do SLAAC. So if you set the M-flag on your RAs, and unset the A-flag then hosts will have to use DHCPv6 to obtain addresses. Of course, this won't stop hosts from unilaterally deciding to transmit packets using any source address that they choose to, but this is no different than with IPv4.