What are four advantages to using tunnel brokers in an IPv6 transition environment?

What are four advantages to using tunnel brokers in an IPv6 transition environment?

A.
Tunnel brokers automatically provide configuration parameters to peer routers.

B.
IPv6 enabling a node looks automatic to the end user.

C.
Tunnel information is sent via IPv4.

D.
Tunnel brokers make it simpler for nontechnical users to deploy manual tunnels.