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

Cisco 4000 Series ISRs target these applications:

• Enterprise applications—Intended for mid-size aggregation and gateway router that is located in a regional or large branch office:

– WAN aggregation at Cisco Enterprise core

– Internet gateway

– Branch or regional office aggregation

– Remote access aggregation

• Service provider applications—Intended for high-end Enterprise Branch environments:

– High-end customer premises equipment (CPE) for business-quality Internet access

– Service provider leased line aggregation

– Provider edge (PE) and high-end customer edge (CE) for Layer 2 VPN or Layer 3 VPN services

– Low-end Ethernet aggregation

Cisco 4000 Series ISRs are available in these models:

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