With the Inter-Gateway Alternate Routing (IGAR) feature, Communication Manager can use the PSTN when the IP-WAN cannot carry the bearer connection for the single-server systems that use the IP-WAN to connect bearer traffic between port networks or gateways.
Note:
Communication Manager Release 6.3.5 and earlier supported IGAR for analog, DCP, and H.323 endpoints. Communication Manager Release 6.3.6 or later extends this support to SIP endpoints.
