I got it to work, the anchored clients gets an IPv6 address from the default router, so that´s fine.
But unfortunately when I´m trying on a 5520, I can´t just enable Global Multicast. When I´m trying, I get:
"Multicast-Unicast mode does not support IGMP/MLD Snopping. Config mode to Multicast-Multicast first"
And when I´m trying this, at "AP IPv6 Multicast Mode" with an IPv6 address, I get:
"Management interface doesn´t have an IPv6 address. Please configure the same before configuring Multicast IPv6 address"
So I need to configure an IPv6 address on the Management interface to get IPv6 anchored clients to work.
Can anyone tell me why this should be needed?