单项选择题 Which configuration component is required to allow a PPP over ATM client to connect to one virtual router for a particular session and to a different virtual router for another session?（）

单项选择题 When controlling the virtual router assignment for a PPP over ATM client, which mechanism does the router use first?（）

单项选择题 An authentication request for a PPP over ATM client has been returned to the router with an address of 255.255.255.254. What does this indicate to the router?（）