Issue

Please find possible options for troubleshooting inbound telephony below:

Product

• Voice

Resolution

1. Inbound number (DID) not bound to correct Distribution Group Check your Distribution Group IP address settings in Voice Management App.
   
2. Firewall or PBX not configured for CM inbound trunk IP addresses Inbound traffic is routed from our dedicated inbound platform. Please allow incoming traffic from:
   
   Inbound10:
   188.94.184.98
   188.94.184.99
   188.94.184.100
   
   Inbound20:
   188.94.185.98
   188.94.185.99
   188.94.185.110
   
3. No correct response to SIP OPTIONS keep alive messages
   If a SIP 503 Service Unavailable error response is received in your PBX logging when trying to make an inbound voice call.
   Our platform is sending so called Keep Alive messages via SIP OPTIONS which need to be acknowledged by a 200 OK from the customer PBX instance.
   This is the principle by which our gateways check if the inbound trunk is still available.
   After updating your config, please wait 3-5 minutes before retesting since our platform requires a successful response in order to resume inbound call delivery.
   
4. Inbound number format
   The number format for inbound calls is always with the "+" symbol.