多项选择题
What information does a router running a link-state protocol use to build and maintain its topological database?（）
A.hello packets B.SAP messages sent by other routers C.LSAs from other routers D.beacons received on point-to-point links E.routing tables received from other link-state routers F.TTL packets from designated routers
多项选择题 OSPF routing uses the concept of areas. What are the characteristics of OSPF areas? （）
多项选择题 Which are valid modes for a switch port used as a VLAN trunk? （）
填空题 流控的三种方式是（）、（）、（）。
