Secure Edge Router for Small Offices – Cisco ISR4321-SEC/K9
Product Overview
The Cisco ISR4321-SEC/K9 is a security-enabled Integrated Services
Router from the ISR 4000 Series, designed for small branch offices
that require high-performance routing, secure WAN access, and
modular expansion. This model includes the SEC license, enabling
advanced security features like Zone-Based Firewall (ZBFW), IPsec
VPN, SSL VPN, and control plane protection. With a base performance
of 50 Mbps, upgradable to 100 Mbps, the ISR4321-SEC/K9 is ideal for
secure branch connectivity, VPN deployment, and basic SD-WAN
readiness.
Product Details
| Specification | Description |
|---|---|
| Product Code | ISR4321-SEC/K9 |
| Series | Cisco ISR 4000 Series |
| Form Factor | 1RU rack-mountable |
| Base Performance | 50 Mbps (upgradeable to 100 Mbps) |
| Built-in Interfaces | 2 x 1G RJ45, Console, USB |
| NIM Slots | 2 x Network Interface Module slots |
| SM Slots | None |
| DRAM | 4 GB (expandable to 8 GB) |
| Flash Storage | 4 GB (expandable) |
| Power Supply | Internal fixed AC |
| Software | Cisco IOS XE |
| Security License Features | ZBFW, IPsec VPN, SSL VPN, Control Plane Policing |
| SD-WAN Support | Yes (with SD-WAN image) |
| Application Visibility | Basic NetFlow/NBAR2 |
| High Availability | Software-based (no dual PSU support) |
Product Features
Includes Security (SEC) license for enterprise-grade firewall and VPN functions
Supports ZBFW, IPsec/SSL VPN, and dynamic routing protocols
Ideal for secure cloud connectivity, remote access, and branch perimeter defense
Modular platform with 2 NIM slots for WAN, 4G/LTE, or voice expansion
Powered by Cisco IOS XE, enabling automation, telemetry, and SD-WAN
Control plane protection and identity-based firewall for enhanced threat defense
Efficient, low-footprint 1RU form factor, optimized for small remote sites
Similar Models Comparison
| Model | Security License | Max Performance | NIM/SM Slots | SD-WAN Ready | Form Factor |
|---|---|---|---|---|---|
| ISR4321-SEC/K9 | Yes | 100 Mbps | 2 / 0 | Yes | 1RU |
| ISR4331-SEC/K9 | Yes | 300 Mbps | 2 / 1 | Yes | 1RU |
| ISR4351-SEC/K9 | Yes | 400 Mbps | 2 / 2 | Yes | 2RU |
| ISR4221-SEC/K9 | Yes | 35 Mbps | 1 / 0 | Yes | 1RU |
Latest ISR Security Models Comparison
| Model | Performance Range | Key Security Features | Best Use Case |
|---|---|---|---|
| ISR4321-SEC/K9 | 50 – 100 Mbps | ZBFW, IPsec, SSL VPN | Secure small branch routing |
| ISR4331-SEC/K9 | 100 – 300 Mbps | Advanced security & SD-WAN | Medium branches needing strong defense |
| ISR4221-SEC/K9 | Up to 35 Mbps | Entry-level security | Micro-branches with basic security |
