单项选择题
The administrator is unable to establish connectivity between two Cisco routers. Upon reviewing the command output of both routers, what is the most likely caust of the problem?（）
A. Authentication needs to be changed to PAP for both routers. B. Serial IP addresses of routers are not on the same subnet. C. Username/password is incorrectly configured. D. Router names are incorrectly configured.
单项选择题 What is valid reason for a switch to deny port access to new devices when port security is enabled?（）
单项选择题 What is the purpose using the traceroute command?（）
单项选择题 Which type of attack is characterized by flood of packet that requesing a TCP connection to a server?（）
