The Cisco 2901 router delivers secure data, voice, video and application services for small offices. It has 2 Ethernet ports, 4 WAN interface card slots, 2 DSP slots, an internal services module, and supports PoE and hardware-accelerated VPN encryption. The 2901 is 1RU in size, often called a 'pizza box' router, and is the successor to Cisco's 2500, 2600 and 2800 series routers. It has limitations on additional modules compared to higher models like the 2911.