单项选择题 IS - IS creates and maintains adjacencies and neighbor relations by using the Hello protocol. For the following options, which are Hello packets used in IS - IS?（）

单项选择题 When learning a new route, if a LSA received is not found in the topological database, what will an internal OSPF router do?（）

单项选择题 One of the most important characteristics of OSPF is Multiple areas. Which statement best describes why this feature is such an important enhancement to earlier routing protocols?（）