In which three cases is a dual-stack IPv6/IPv4 router required? (Choose three.)
A.
tunnel endpoint routers in the case of IPv6 over GRE
B.
transit routers in case of an IPv6 over GRE implementation
C.
6to4 implementation border routers
D.
6to4 implementation border and neighboring routers
E.
PE routers in case of an IPv6 over IPv4 tunnel over MPLS implementation
F.
PE and P routers in case of an IPv6 over IPv4 tunnel over MPLS implementation