Introduction: SIP or H.323 trunks are the most common VoIP trunks deployed today to interconnect to the outside world (i.e. the Public Switched Telephone Network / PSTN) or to talk between IP PBXes (such as between UC500s at multiple sites). The UC500 supports standards based SIP or H.323 trunks. SIP trunks are the most popular choice today as an IP based PSTN interconnect for a variety of reasons.To make SIP Trunk deployments to UC500 simpler, the CCA tool provides a drop down with a list which includes AT&T IP FlexReach service which has been interop tested and included within the CCA 1.8 tool.
Below are a number of links to help you undestand how to configure the UC500 to work with AT&T's FlexReach Service.