At our remote location we are going to transfer our 4 VoIP phones from ISP A to ISP B. At the main location is the VoIP server that the remote phones connect to. The main location uses ISP A to connect to the remote location through a VPN tunnel, where the remote phones can connect to the VoIP server. My question is do we need to connect another router to ISP B to allow the VoIP phones to communicate with the main location server? And if so will need a special configuration to communicate with that server? Also do we need to create a VPN tunnel between Remote ISP B router to main ISP A router?
Any help would be greatly appreciated!