A．Router (config) #interface a1
Router (config-if) #encapsulation ppp
Router (config-if) #async default ip address 195.223.56.16
Router (config-if) #exit
Router (config) #interface s1/1
Router (config-if) #ip address 222.112.41.81 255.255.255.252
Router (config-if) #encapsulation ppp
B．Router (config) #interface a1
Router (config-if) #encapsulation ppp
Router (config-if) #asyne default ip address 195.223.56.16
Router (config-if) #exit
Router (config) #interface s1/1
Router (config-if) #ip address 222.112.41.81 255.255.255.252
Router (config-if) #encapsulation hdlc
C．Router (config) #interface a1
Router (config-if) #encapsulation ppp
Router (config-if) #async default ip address 195.223.56.17
Router (config-if) #exit
Router (config) #interface s1/1
Router (config-if) #ip address 222.112.41.81 255.255.255.252
Router (config-if) #encapsulation ppp
D．Router (config) #interface a1
Router (config-if) #encapsulation hdlc
Router (config-if) #async default ip address 195.223.56.17
Router (config-if) #exit
Router (config) #interface s1/1
Router (config-if) #ip address 222.112.41.81 255.255.255.252
Router (config-if) #encapsulation ppp