单项选择题 The ERX Edge Router is configured for PPP over Ethernet without using VLAN tagging. How many PPP over Ethernet major interfaces can be configured per port?（）

单项选择题 Which process occurs first during the Ethernet Discovery Stage process for a PPPoE service offering?（）

单项选择题 A user is connected on a DSL line and is using a PPP over Ethernet service. Which network device encapsulates the datagram inside of an ATM header?（）