The common telephone line is changed to the backup line of special line using the function of Cisco router Dail-on-demand routing (DDR).是什么意思_The common telephone line is changed to the backup line of special line using the function of Cisco router Dail-on-demand routing (DDR).在線(xiàn)翻譯_英語(yǔ)_讀音_用法_例句