单项选择题 A company has a Frame Relay WAN with one central - site router and 100 branch office routers. A partial mesh of PVCs exists: one PVC between the central site and each of t he 100 branch routers. All routers use point - to - point subinterfaces and one subnet per PVC. Which of the following is true about OSPF in this design?（）

单项选择题 Which of the following settings do not prevent two potential OSPF neighbors from becoming neighbors?（）

多项选择题 Routers R1 and R2, OSPF neighbors in area 0 over their Fa0/0 interfaces (respectively), currently both successfully use OSPF MD5 authentication. The OSPF configuration includes the area 0 authentication command under the router ospf 1 command. Which of the following commands must have been configur ed on R1s Fa0/0 interface?（）