The Cisco 4000 series routers run Cisco IOS software, Cisco's industry-leading networking software that provides a variety of feature sets. You can choose a feature set that supports your specific protocol environment. Cisco IOS software assures robust, reliable internet works by supporting both LAN and WAN protocols, optimizing WAN services, and controlling internet work access. In addition, Cisco IOS software allows centralized, integrated; and automated installation and management of internet works. The Cisco 4000 series routers offer Flash EPROM technology as a standard feature. Flash EPROMs enable you to distribute new software releases from a central location. After the software is distributed, the routers can reboot from programs stored in local Flash memory.All models provide a configurable modular router platform by using network processor modules (NPMs) - individual removable cards used for external network connections. Because the router's modules support many variations of protocols, line speeds, and transmission media, the Cisco 4000 series can accommodate all types of network computing environments. As Cisco introduces new modules, the Cisco 4000 series can be upgraded to keep pace with technological advances.