How to Reserve an Extension Number Last updated Save as PDF Share Share Tweet Share Loading...8x8 & COVID-19: Protecting Our Business and YoursBusiness closed for the holidays? Get ready with our tips!PrevNext 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.