The Cisco 4000 Series ISRs are modular routers with LAN and WAN connections that can be configured by means of interface modules, including Cisco Enhanced Service Modules (SM-Xs), and Network Interface Modules (NIMs). NIM slots also support removable storage for hosted applications.

The following features are provided for enterprise and service provider applications:

• Enterprise Applications

  • High-end branch gateway

  • Regional site aggregation

  • Key server or PfR primary controller

  • Device consolidation or "Rack in a Box"

• Service Provider Applications

  • High-end managed services in Customer-Premises Equipment (CPE)

  • Services consolidation platform

  • Route reflector or shadow router

  • Flexible customer edge router

The router runs Cisco IOS XE software, and uses software components in many separate processes. This modular architecture increases network resiliency, compared to standard Cisco IOS software.