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 (Choose three.)（）。
A.FTP B.Telnet C.SMTP D.DNS E.HTTP F.POP3
多项选择题 What are two benefits of using NAT?（）
单项选择题 What is the purpose using the traceroute command?（）
单项选择题 On which types of network will OSPF elect a backup designated router（）。
