Overview of Cisco 4000 Series ISRs

The Cisco 4000 Series Integrated Services Routers (ISRs) are modular routers offering LAN and WAN connectivity. They support various interface modules, including Cisco Enhanced Service Modules (SM-X) and Network Interface Modules (NIMs).

These ISRs are designed for two primary application areas:

• Enterprise applications: Suitable for mid-size aggregation and gateway routing in regional or large branch offices. Applications include WAN aggregation, internet gateway, branch/regional office aggregation, and remote access aggregation.
• Service provider applications: Designed for high-end Enterprise Branch environments. Use cases include customer premises equipment (CPE) for business-quality internet access, service provider leased line aggregation, provider edge (PE) and customer edge (CE) for VPN services, and low-end Ethernet aggregation.

Available models include:

• Cisco 4461 ISR
• Cisco 4451-X ISR
• Cisco 4431 ISR
• Cisco 4351 ISR
• Cisco 4331 ISR
• Cisco 4321 ISR
• Cisco 4221 ISR

This documentation applies to all Cisco 4000 Series ISR models unless a specific model is mentioned.