What are three IPv6 transition mechanisms?

What are three IPv6 transition mechanisms? (Choose three)

A.
6to4 tunneling

B.
VPN tunneling

C.
GRE tunneling

D.
ISATAP tunneling

E.
PPP tunneling

F.
Teredo tunneling

Explanation:
Below is a summary of IPv6 transition technologies:
6 to 4 tunneling: This mechanism allows IPv6 sites to communicate with each other over the IPv4
network without explicit tunnel setup. The main advantage of this technology is that it requires no
end-node reconfiguration and minimal router configuration but it is not intended as a permanent
solution.
ISATAP tunneling (Intra-Site Automatic Tunnel Addressing Protocol): is a mechanism for
transmitting IPv6 packets over IPv4 network. The word “automatic” means that once an ISATAP
server/router has been set up, only the clients must be configured to connect to it.
Teredo tunneling: This mechanism tunnels IPv6 datagrams within IPv4 UDP datagrams, allowing
private IPv4 address and IPv4 NAT traversal to be used.
In fact, GRE tunneling is also a IPv6 transition mechanism but is not mentioned in BSCI so we
shouldn’t choose it (there are 4 types of IPv6 transition mechanisms mentioned in BSCI; they are
manual, 6-to-4, Teredo and ISATAP).