<p>QUESTION NO: 21 On the topic of ospf ; which of the following are the traits of an ospf area? (Select all that apply)</p><p>A. Each OSPF area requires a loopback interface to be config</p><p>B. Areas may be assigned any number from 0 to 65535.</p><p>C. Area 0 is called the backbone area.</p><p>D. Hierarchical OSPF networks do not require multiple areas</p><p>E. Multiple OSPF areas must connect to area 0.</p><p>F. Single area OSPF networks must be configured in area 1.</p><p>答案D好象也没问题啊,怎么不对啊</p><p> </p>