多项选择题
A. OSPF sends updates every 10 seconds
B. OSPF sends triggered updates when a network change occurs
C. When a link state is changed, the router that detected the change creates a link - state advertisement (LSA) and propagates it to all OSPF devices using the 224.0.0.6 multicast address
D. OSPF sends summaries of individual link- state entries every 30 minutes to ensure LSDB synchronization
单项选择题 OSPF is configured over a Frame Relay network as shown in the exhibit. All PVCs are active.However, R1 and R3 fail to see all OSPF routes in their routing tables. The show ip ospf neighbor command executed on R2 shows the state of t he neighbors. What should be done to fix the problem? （）
单项选择题 Refer to the exhibit. During the process of configuring a virtual link to connect area 2 with the backbone area, the network administrator received this console message on R3: *Mar 1 00:2 5:01.084: %OSPF -4- ERRRCV: Received invalid packet: mismatch area ID, from backbone area must be virtual link but not found from 20.20.20.1, Serial 0 .How should the virtual link be configured on the OSPF routers to establish full connectivity between the areas?（）
单项选择题 DR (Designated Router) is for environments where many routers on the same network such as Ethernet. In the following presented network, all routers are reloaded simultaneously, and DR is selected as expected. What is the RTC status?（）