多项选择题
OSPF协议定义了5种网络类型，哪些类型的网络需要选举网络Designated Router（DR）、BackupDesignated Router（BDR）（）？
A.Point-to-point B.Nonbroadcast multi-access C.Point-to-multipoint D.Broadcast multi-access
多项选择题 You are the administrator of the large OSPF network and are considering dividing it to multiple areas.What are two advantages of configuring multiple OSPF areas（）？
多项选择题 Which of the following are features are characteristics of an OSPF ABR（）。
多项选择题 OSPF没有形成FULL状态的原因有哪些（）。
