Trunk Group Registration allows you to bind an endpoint to a specific trunk and configure the authentication settings. This can be found in any Trunk Group by selecting the Registration option from the drop down list that shows the IP Address options by default as show in the image below:
Once you have configured the username, password and selected switch IP that you would like to use for authentication click on the Create button.
Next, enter that same authentication information and IP address into your endpoint (softphone, etc). Once this is done, if your trunk group has proper routing and rating, your registration will allow you to make calls!
Note:Bound IP: A user can register an IP address to bind to the Registration or use network masks to whitelist a range of IPs by entering a mask alongside the IP such as 192.168.1.0/23. The valid masks would therefore be from 22 to 31. During the registration process, if an IP was configured then the platform will verify the registration request is coming from the appropriate IP.