When two or more Controllers are configured in XCAPI, it is not possible to add the second or subsequent controller in the GFI FaxMaker configuration.
Confirm that each controller has a unique combination of these three parameters:
Network card: if the server has multiple NICs, you can simply select different cards for each controller under Controller > Network
IP address: if the server only has one NIC, you can assign multiple IP addresses manually and then select the individual addresses under Controller > Network
Local listening port (this is what needs to be changed in most scenarios):
IF you will be using H.323, go to H.323 > Gateway > Extended Options and use different local ports for each controller. On a SIP controller, you can find that setting under Controller > SIP > Protocol > Local Port for UDP/TCP.
IF a VOIP gateway is being used, ensure that the calls are routed to the correct IP address on the XCAPI server (e.g. calls to controller 1 should be routed to 184.108.40.206:5060 and calls to controller 2 should be routed to 220.127.116.11:5061)
IF SIP trunks are being used with an internet SIP provider, no additional configuration is needed normally, because XCAPI informs the provider on the address:port configuration during the SIP REGISTER phase
This is a common problem when using multiple controllers on one system. The controllers share three attributes which can cause this problem: the network interface card, the IP address, and the local listening port.