多项选择题
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?（）
多项选择题 An inbound access list has been configured on a serial interface to deny packet entry for TCP and UDP ports 21, 23 and 25. What types of packets will be permitted by this ACL?（）