In IPv6 network, an IPv6 overlay tunnel is required to communicate with isolated IPv6 networks across the existing IPv4 infrastructurE. There are currently fiv e IPv6 overlay tunnel types. Which three IPv6 overlay tunnel statements are true？（）

• A、Overlay tunnels can only be configured between border routers capable of supporting IPv4 and IPv6.
• B、An manual overlay tunnel supports point - to - multipo int tunnels capable of carrying IPv6 and Connectionless Network Service (CLNS) packets.
• C、Overlay tunneling encapsulates IPv6 packets in IPv4 packets for delivery across an IPv4 infrastructure.
• D、Overlay tunnels can be configured between border route rs or between a border router and a host capable of supporting IPv4 and IPv6.
• E、Cisco IOS supports manual, generic routing encapsulation (GRE), IPv4 - compatible, 6to4, and Intra - Site Automatic Tunnel Addressing Protocol (ISATAP) overlay tunneling mechan isms.
• F、Cisco IOS supports manual, generic routing encapsulation (GRE), IPv6 - compatible, 4to6, and Multiprotocol Label Switching (MPLS) overlay tunneling mechanisms.