Replace your Carrier Remote or Mini Carrier Remote with an Avaya Survivable Media Gateway (SMG). The SMG connects to your main PBX through the corporate WAN. Furthermore, the SMG will operate in survival mode during a WAN failure. During a network failure, the SMG will support phone operation by engaging its own CPU. This is something your Carrier Remote cannot do. In addition, the SMG is IP based which means it will register with your main-site PBX. Therefore, if you are paying a T1 carrier in order to support your Carrier Remote or Mini Carrier Remote Cabinet, upgrade your main site to Avaya release 7.6 and install a Survivable Media Gateway.

“Survivable Media Gateway enhances the reliability of Avaya Communication Server 1000E (Avaya CS 1000E) systems by allowing the provisioning of up to 50 geographically remote Secondary Call Servers to a Primary Call Server. You can configure each Secondary Call Server as Alternate Call Server 1 or Alternate Call Server 2 for the devices assigned to it. Survivable Media Gateway provides two levels of redundancy. If the Primary Call Server fails, local and remote resources register with the Secondary Call Server configured as Alternate Call Server 1. If the Primary and Secondary Call Servers both fail, or the WAN fails, local resources register with the Secondary Call Server that is installed at the local site and configured as Alternate Call Server 2.”

Reference: NN43001-507_06_01_System_Redundancy_Fundamentals