A. When Area 0 is active, the loopback interface must be configured in OSPF for it to be advertised.
B. When Area 0 is active, the loopback address is automatically advertised into other areas.
C. When Area 0 is active, the OSPF router-id must match the loopback address for the loopback address to be advertised.
D. When Area 0 is active, the router-id must be configured for the loopback address to be advertised.
参考答案：A
