单项选择题 Which CLI command displays the currently connected PPPoA subscribers?（）

单项选择题 End users are failing to log in to the network. Which command is used on the ERX Edge Router to validate communications with the RADIUS server?（）

单项选择题 The output of the show aaa domain-map displays the following information: Domain: isp1.com; virtual-router: vr1; loopback: 1 Domain: isp2.com; virtual-router: vr2; loopback: 1 Domain: none; virtual-router: vr3; loopback: 1 Domain: default; virtual-router: vr4; loopback: 1 The end user supplies a login name of joe@isp7.com . Which virtual router is responsible for authenticating this user?（）