ng Part 2 of this book provided detailed coverage of all the planning activities, Session Initial Protocol (SIP) trunk models, SIP trunk evaluation questions, and interworking and network design information necessary to prepare for a SIP trunk installation into your network. The chapters in Part 3 look much more closely at the actual deployment and implementa- tion of a SIP trunk and the configurations necessary to interconnect equipment and net- works. This chapter covers configurations for the typical SIP trunk deployment scenarios and helpful implementation notes for each of these. The connectivity and features needed in different deployment scenarios vary. SIP trunk deployments covered in this chapter are shown in Figure 10-1, including the following: Enterprise SIP Trunk for Public Switched Telephone Network (PSTN) Access Small-Medium Business (SMB) SIP Trunk for PSTN Access Enterprise SIP Trunk for PSTN Access There are already many SIP trunk service provider (SP) globally offering services, and undoubtedly, more will add services as time goes by. The offerings vary from one another, SO it is difficult to give a single configuration that enables implementation of a SIP trunk with any SP. Two interoperability examples are given in the following sections. These examples are AT&T and Verizon because they were two of the first to market with a 192 SIP Trunking business-class offering and are therefore more known quantities at this time. Even if you connect to a different provider's offering, reading through these configurations can be helpful for the type of configuration commands you might require to configure your bor- der element to interconnect with the SP of your choice. SP IP Network Enterprise CUCM 6.x or 7.x SIP Trunk for PSTN Access H.323 SP IP Network CUCM 4.x or 5.x SMB SIP Trunk for SP IP Network Access CUCME Figure 10-1 SIP Trunk Deployment Scenarios The following implementations are discussed in this section: Connecting Cisco Unified Communications Manager (CUCM) using SIP to an AT&T FlexReach SIP