According to RFC 4577, OSPF for BGP/MPLS IP VPNs, when must the down bit be set?
A.
when an OSPF route is distributed from the PE to the CE, for Type 3 LSAs
B.
when an OSPF route is distributed from the PE to the CE, for Type 5 LSAs
C.
when an OSPF route is distributed from the PE to the CE, for Type 3 and Type 5 LSAs
D.
when an OSPF route is distributed from the PE to the CE, for all types of LSAs