A call loop occurs when call forwarding rules are set up in a way that allows a single call to go back to a destination infinitely, without allowing the call to reach a voicemail box.
Call loops are bad because they can cause problems for the PBX, and cause missed calls, which is the opposite of the intent when creating forwarding rules. When you create a call loop and calls start coming in, this create logs in the server. Since the loop is infinite, so are the logs. The means it is possible to crash your PBX if a call gets forwarded too many times. Also, when a loop is in place, additional calls that hit the loop often receive a fast busy signal when dialed, preventing you from answering that call.
Call Loop Examples
Example 1: Auto Attendant Forwarding to Ring Group
The most common example we see is having the Ring Group forward to the Auto Attendant, only to have the Auto Attendant forward back to the Ring Group. That looks like this:
A caller dials a Virtual Number, which gets forwarded to an Auto Attendant, which forwards calls to the Ring Group. The Ring Group has a no answer or busy forwarding rule, which forwards the call to the Auto Attendant.
The call will then be sent from the Ring Group to the Auto Attendant in an endless cycle.
Example 2: Extension Forwarding to a Ring Group
A caller dials a Virtual Number, which gets forwarded to an Extension, which has a forwarding rule to send the call to a Ring Group if the line is busy or if there is no answer. The Ring Group has a no answer or busy forwarding rule to send the call to the Extension.
The call is then stuck in a loop between the Extension and the Ring Group.
Example 3: Using Forwarding Settings on Physical Phones
A caller dials a Virtual Number, which is forwarded to Extension x1001 that has a no answer forwarding rule, which sends calls to the original Virtual Number.
As these calls are stored locally to the phone, 8x8 cannot detect them in the system.