The Anywave Network-In-a-Box cellular system has been used by military customers to integrate commercial cellular communications into their existing telephone networks. The combination of flexible software with COTS hardware provides a low-cost solution that supports a wide variety of network interfaces. This paper describes the integration of a Network-In-a-Box system into two different military telephone networks, and discusses some of the design and integration challenges faced. A key component of the integrated solution is the Asterisk open-source PBX application. The first case study shows how Asterisk can be easily used to connect the VoIP-based Network-In-a-Box system to a legacy T1 telephone network. The second case study describes how the standard Network-In-a-Box was enhanced with Type 1 secure communication capabilities in order to interconnect a GSM cellular network with a classified VoIP network.