选择题：In IPv6 network, an IPv6 overlay tunnel is required to communicate with isolated IPv6 netw

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.