VoIP Trunks require specific ports open on your firewall in order to operate normally. Please read about Port Forwarding.
If your VoIP account requires advanced configuration (e.g. DTMF, audio codec priority, etc.) click the + symbol next to the word Advanced to access additional configuration options.
NOTE: The majority of customers should leave every option under Advanced at its default value. Unless explicitly instructed by your VoIP Provider, all default settings are "known good".
Do you have enough bandwidth? VoIP calls using the most common codec - g711 ulaw - require approximately 80 kilobits (kb) of bandwidth for a single call. If you would like to figure out how many calls your Internet connection can support, simply divide the speed of your connection by 80.
Example: 1.5 MBps = 1500 kbps / 80 = 18.75 or 18 maximum calls assuming the Internet is not being used for ANYTHING else.
Required to be able to receive calls.