FR的一道题目

荷兰的桔子

If required，what password should be configured on the router in the pass4sure2 branch office to allow a connection to be established with the pss4sure1 router?
A.no password is required
B.enable
C.telnet
D.secret
E.console
如果2和1是通过ppp接口连接的那么应该选哪个？