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?（）

A. The interface used to connect to that neighbor being passive in the OSPF process
B. Duplicate OSPF router IDs
C. Mismatched dead timers
D. IP addr esses of 10.1.1.1/24 and 10.2.2.2/24
E. Mismatched OSPF process IDs

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?（）

A. ip ospf authentication null
B. ip ospf authentication message - digest
C. ip ospf authentication -key whatever- it - is
D. ip ospf message - digest - key 1 md5 whatever - it - is
E. ip ospf md5 1 key whatever - it - is

多项选择题Routers R1 and R2 are OSPF neighbors using their Fa0 0 interfaces, respectively, using default settings for all timers. An engineer ad ds the ip ospf hello - interval 6 command to R1s Fa0 0 configuration. Which of the following is true regarding the results from this change?（）

A. The show ip ospf neighbor command on R1 lists the revised Hello timer
B. The show ip ospf interfac e brief command on R1 lists the revised Hello timer
C. The R1 - R2 neighborship fails due to Hello timer mismatcH
D. The show ip ospf interface command on R1 lists the revised Hello timer

多项选择题Rout er R1 directly connects to subnet 10.1.1.0 24 with its Fa0 0 interface. R1 can ping four other working OSPF routers in that subnet. R1 is neither the designated router (DR) nor backup DR (BDR). OSPF is working correctly on all five routers. Which of the following is true on R1?（）

A. The show ip ospf neighbors command lists two neighbors off Fa0/0.
B. The show ip ospf neighbors command lists four neighbors off Fa0/0.
C. The show ip ospf neighbors command lists two neighbors off Fa0/0 in the FULL state.
D. The show ip ospf neighbors command lists two neighbors off Fa0/0 in the DISCO state.

多项选择题Which of the following can either directly or indirec tly identify all the interfaces for which both 1) OSPF has been enabled and 2) OSPF is not passive?（）

A. show ip ospf database
B. show ip ospf interface brief
C. show ip protocols
D. show ip route ospf
E. show ip ospf neighbors