IPv6 computing a global unicast address
An IPv6 interface will compute its global unicast IPv6 address only if the ipv6 address autoconfig
command is issued AND there is an active IPv6 router on that subnet. The autoconfig
keyword enables autoconfiguration or SLAAC.
Links:
https://networklessons.com/ipv6/cisco-dhcpv6-server-configuration/
https://forum.networklessons.com/t/cisco-dhcpv6-server-configuration/1116/66?u=lagapides