单项选择题
A.traceroute address
B.tracert address
C.ssh address
D.telnet address
单项选择题 出于安全考虑，网络管理员需要去防止外网主机PING内网，下面哪个协议应该用access control lists限制掉？（）
单项选择题 A company has a small network，consisting of a single switch and a single router. The switch has been configured with two vlans，and route-on-a-stick is being configured on the router for inter-vlan routing. A trunk is configured to connect the switch to the router.What is the minimum number of router subinterfaces that are required for all the vlans to communicate？（）
多项选择题 What can a network administrator utilize by using PPP Layer 2 encapsulation (Choose three.) （）。