If you are a voice network engineer, then it has probably happened to you. Your SIP server is all set up and you have plugged in your IP phone. Its lights come on, its screen is activated, you see the loading icon rotating, and then… nothing. For some reason, the phone will not register.
IP phone registration issues are, unfortunately, not uncommon. In this article, we examine the most common causes of registration failures, and best practices for troubleshooting and resolving them.