单项选择题
A. Only routers can split boundaries (horizons) between concentric networks.
B. Each AS must keep routing tables converged to prevent dead routes from being advertised across boundaries.
C. Networks can only remain fully converged if all information is sent out all active interfaces.
D. Information about a route should not be sent back in the direction from which the original update came.
E. Distance vector protocols need fall back routers that are responsible for momentary loops.
单项选择题 What kind of packets does OSPF send to keep up connectivity with its neighboring routers?（）
多项选择题 What kind of information does a router running a link-state routing protocol need to create and maintain its topological database?（）
单项选择题 In a point-to point network, which address are OSPF hello packets sent to?（）