How to Reserve an Extension Number Last updated Save as PDF Share Share Tweet Share Loading...8x8 Support impacted by local COVID-19 measures. Please create a case online for the best help.Recently upgraded to 8x8 Video Meetings? Click here!Some US Landline Participants get a Busy Signal in 8x8 Video MeetingsPrevNext Objective To reserve an extension number in Configuration Manager. Applies To Configuration Manager Extensions Procedure Log into Configuration Manager. Click Extension Numbers. Click Reserve Extension Numbers (top right). Complete the fields, as seen below. Click Save. Best Practice It is best practice that the below extension numbers marked as reserved are not used.