Under extensions>advanced settings, I’d like to permit a specific IP range which is the IP from the SIP provider. Is there a way to apply this to all extensions at once? Or do you have to apply it one extension at a time?
extensions>advanced settings looks like a menu navigation path. Asterisk does not have any GUI, so there are no menus.
If these are GUI menus, please contact the people that developed the GUI that is running on top of Asterisk. This is most likely FreePBX. Peer support for that is available at https://community.freepbx.org/
Also, asterisk extensions are numbers. They do not have IP addresses.