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?（）

单项选择题 The router receives a login request from a PPP over ATM client and examines the domain map for the clients domain. The router finds no entries currently configured within the domain map. What does the router do with the login request?（）

单项选择题 By default, which PPP mechanism does the ERX Edge Router use to monitor the session for a PPP over ATM client?（）