Use the hs-v6avail command from the hotspot context to configure the hotspot ANQP IPV6 availability.
(NA|available|unknown) | The mobile device uses the IP Address Type Availability information to make network selection decisions. Specify the level of restriction for the IPV6 network. |
EWC.extremenetworks.com:wlans:hs:hotspot# hs-v6avail public