多项选择题
A. Host 1 on VLAN 1 can ping Host 2 on VLAN 1
B. Host 1 on VLAN 1 can ping Host 4 on VLAN 2
C. Host 1 on VLAN 1 can not ping Host 2 on VLAN 1
D. Host 4 on VLAN 2 can not ping Host 1 on VLAN 1
E. Host 4 on VLAN 2 can ping Host 2 on VLAN 2
单项选择题 A TestKing.com technician is troubleshooting connectivity problems between two routers that are directly connected through the serial line. The technician notices that the serial line is up but cannot see any neighbors displayed in the output of the show cdp neighbors command. In which OSI layer is the problem most likely occurring?（）
单项选择题 Which layer of the OSI reference model is responsible for ensuring reliable end-to-end delivery of data?（）
单项选择题 You download a file from an FTP site on the Internet. What is the highest layer in the OSI model used in this FTP operation?（）