The Cisco MCS 7835-I2 Unified Communications Manager Appliance (MCS 7835-I2) is a high-availability server platform for Cisco Unified Communications Manager 6.0 or 5.1 and greater and an integral part of a complete, scalable architecture for a new generation of high quality unified communications solutions for enterprise data networks. Delivering the high performance and availability that today's enterprise networks demand, the solution is easy to deploy and highly cost effective. The server appliance is preinstalled with an operating system and Cisco Unified Communications Manager 6.0 or 5.1. Cisco Unified Communications Manager was formerly known as Cisco Unified CallManager. It is fully operational upon startup, requiring entry of just a few configuration items such as IP address and domain. At just 2 rack units (2RU) high, the Cisco MCS 7835-I2 Unified Communications Manager Appliance packs tremendous power in a low-profile chassis that minimizes rack space. It can support up to 2500 Cisco Unified IP phones per server and 10,000 Cisco Unified IP phones per cluster.