ISR4321/K9 Lightweight Enterprise Router with Performance-on-Demand
Product Overview
The Cisco ISR4321/K9 is a compact, high-performance integrated
services router from the Cisco ISR 4000 Series, specifically
designed for small branch offices. It delivers essential services
such as routing, VPN, voice, and application optimization, with
built-in modularity, SD-WAN readiness, and performance scalability
from 50 Mbps to 100 Mbps via license. This router is ideal for
businesses needing cost-effective, secure, and reliable WAN
connectivity with future-ready expandability.
Product Details
| Specification | Description |
|---|---|
| Product Code | ISR4321/K9 |
| Series | Cisco ISR 4000 Series |
| Form Factor | 1RU Rack-Mountable (compact depth) |
| Default Throughput | 50 Mbps (upgradable to 100 Mbps via license) |
| Processor | Cisco QuantumFlow Processor |
| System Memory (DRAM) | 4 GB (upgradeable to 8 GB) |
| Flash Storage | 4 GB (upgradeable to 32 GB) |
| Integrated GE Ports | 2 x 1G RJ45 + 1 x 1G SFP |
| NIM Slots | 2 |
| SM-X Slot | None |
| Voice Support | Optional with DSP and UC license |
| Security Support | Available with SEC license (not included in base model) |
| SD-WAN Capable | Yes |
| Redundant Power Supply | No |
| Software | Cisco IOS XE (modular, programmable OS) |
| Virtualization Support | Yes (supports KVM and containers) |
Product Features
Performance-on-Demand license allows throughput scaling (50–100 Mbps)
Integrated Gigabit Ethernet ports with flexible WAN and LAN configurations
Modular design with NIM slots for LTE, T1/E1, DSL, FXO/FXS, and serial options
Optional support for voice DSPs, SRST, CME, and Unified Communications
SD-WAN ready for cloud on-ramp, application-based routing, and WAN segmentation
Supports IPsec VPN, ZBFW, and application visibility (with licenses)
Ideal for secure and scalable branch connectivity in space-constrained locations
Similar Models Comparison
| Model | Default Throughput | Max Throughput | NIM Slots | Voice Capable | SD-WAN | Ideal Use Case |
|---|---|---|---|---|---|---|
| ISR4331/K9 | 100 Mbps | 300 Mbps | 2 | Optional | Yes | Small/medium branch office |
| ISR4321/K9 | 50 Mbps | 100 Mbps | 2 | Optional | Yes | Small branch connectivity |
| ISR4221/K9 | 35 Mbps | 75 Mbps | 2 | Optional | Yes | Entry-level secure routing |
Latest ISR 4000 Series Overview
| Model | Max Throughput | Form Factor | SD-WAN | Voice Capable | Ideal Use Case |
|---|---|---|---|---|---|
| ISR4331/K9 | 300 Mbps | 1RU | Yes | Optional | Medium branch WAN + security |
| ISR4321/K9 | 100 Mbps | 1RU compact | Yes | Optional | Small branch offices |
| ISR4221/K9 | 75 Mbps | 1RU compact | Yes | Optional | Entry-level remote branches |
