多项选择题
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?（）
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?（）
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?（）