我在配置ADSL配置拨号上网时输入sudo pppoeconf 输入了帐号和密码后找到了两台设备然后选是，接着就出现下面这个提示
NOT CONNECTED
Sorry,I scanned 1 interface(s),but the Access
Concentrator of your provider did not respond.Please check your network and modem cables.Another reason for the scan failure may also be another running pppoe process which controls the modem.
请问这是什么原因，该怎么解决，谢谢！！
