单项选择题
Which encapsulation type is a Frame Relay encapsulation type that is supported by Cisco routers?（）
A.IETF B.HDLC C.Q9333-A Annex A D.ANSI Annex D
单项选择题 Which layer 2 protocol encapsulation type supports synchronous and asynchronous circuis and has built-in security mechanisms?（）
多项选择题 Which two options are valid WAN connectivity methods?（）
单项选择题 At which layer of the OSI model dose PPP perform?（）
