If your network is protected by firewall which restrict outbound traffic please ensure you allow the following addresses and ports combinations:
North and South America, Asia and Oceania:
Europe and Africa:
Note: although normally your SIP endpoints will be assigned to one of the locations above (based on your geographical location) in unlikely even of one of GoTrunk data centres becoming unavailable your traffic will be redirected to the other location (via automated SIP fail over mechanism). It is therefore important to allow traffic to all above listed IP addresses.