Allowed Addresses
IP, MASK – permits traffic from this IP only. You can find a detailed explanation here.
You can enable multiple allowed addresses however this option should be turned on to be visible in main device settings window. Go to SETTINGS -> Setup -> Settings -> Various tab and choose Yes for Enable "Allowed addresses" option for Devices:.
And click Save changes.
Now, when pressed on Advanced button, you will see an additional section in SIP and IAX2 Devices edit window:
Allowed addresses describes from what IP's or defined subnets accept traffic.
NOTE that this setting take effect only for Dynamic authentication devices. For IP authentication devices, this setting is not applied.
If you do not clearly understand what these settings are used for, leave them with default values.
