Cisco ISR4331/K9 Full English Product Description

Product Overview

TheCisco ISR4331/K9is a 1RU rack-mountable integrated services router belonging to the Cisco ISR 4000 Series, built for small-to-medium enterprise branch offices, retail sites, and remote campus edge deployments. Powered by Cisco IOS XE and a multi-core separation-plane architecture (data, control, services), it converges high-performance routing, SD-WAN, embedded security, unified communications, and edge virtualization on a single compact chassis, eliminating the need for multiple standalone branch appliancesCisco. This base AC-powered SKU (ISR4331/K9) operates on standard 100–240 VAC mains power, distinct from the DC variant ISR4331-DC/K9 for telecom rack environments.

ISR4331/K9 Front Panel Layout

Core Hardware Specifications

Built-in Interfaces

1× Combo Gigabit Ethernet port (RJ45 copper or SFP fiber shared slot)
1× Fixed GE RJ45 LAN/WAN port
1× Fixed GE SFP fiber-only uplink port
1× USB 2.0 Type-A port for storage and ZTD provisioning
Dual console ports: Mini-USB Type B + RJ45 serial console; RJ45 auxiliary port for remote out-of-band access

Expansion Slots

2× NIM (Network Interface Module) slots for modular WAN/LAN expansion (T1/E1, xDSL, PoE switch modules, 10G fiber)
1× Single-wide SM service module slot for high-density switching blades or voice DSP modules
1× Internal ISC slot for crypto acceleration or dedicated service engines

Memory & Processing

Multi-core dedicated CPU with separated data/control/services planes
Default: 4 GB ECC DDR3 DRAM, expandable up to 16 GB maximum
Default: 4 GB industrial flash storage, upgradable to 16 GB for IOS XE images, logs, and virtual workloadsCisco Russ...

Throughput Performance

Base unlicensed aggregate throughput: 100 Mbps
Upgradable to 300 Mbps with Performance license
Boost license enables encrypted throughput up to 2 Gbps for heavy VPN/security workloadsCisco Russ...

Physical & Power

Form factor: 1 Rack Unit (1RU), standard rack-mount bracket included
Internal single AC power supply; redundant power not supported on ISR4331 chassis
Input: 100–240 VAC auto-ranging, 47–63 Hz input frequency

Key Functional Capabilities

1. SD-WAN & Intelligent WAN (IWAN)

Fully integrated Cisco IOS XE SD-WAN stack supporting multi-link hybrid WAN (MPLS, broadband 4G/5G LTE, fiber), application-aware routing, traffic steering, path quality monitoring, and centralized orchestration via vManage or Cisco DNA Center. Enables zero-touch deployment (ZTD) for mass branch rollouts.

2. Embedded Integrated Security

Hardware-accelerated IPsec, SSL VPN, AES-256 encryption
Zone-based firewall, intrusion prevention (IPS), URL filtering, malware defense
Trustworthy Systems secure boot, runtime integrity, FIPS 140-2 certified crypto modules
Secure direct internet breakout at branches to reduce central data center backhaul loadNIST Compu...

3. Unified Communications (UC)

Compatible with PVDM4 digital signal processor modules to deliver VoIP, video conferencing, PSTN trunking, and remote phone support for branch telephony deployments.

4. Enterprise NFV Virtualization

Supports Cisco NFVIS virtualization infrastructure, allowing deployment of virtual network functions (vFW, vRouter, WAN optimization, cloud monitoring agents) directly on the router without external servers, cutting branch hardware footprint and operational costsCisco.

5. Modular Scalability

Hot-swappable OIR-compliant NIM and SM modules allow in-service WAN/LAN upgrades without chassis reboot, supporting flexible connectivity including serial leased lines, cable broadband, and integrated PoE switch blades for local access devices.

Software & Licensing

Runs modern modularCisco IOS XEoperating system, licensed via a flexible subscription stack:

Base IP Base routing feature set (static routing, OSPF, EIGRP) included
Optional add-on licenses: Performance Boost, Security, SD-WAN, DNA Advantage, Unified Communications
Lifecycle note: ISR4331/K9 reached End-of-Life; official Cisco TAC support terminates November 30, 2028; recommended replacement model: Cisco C8200-1N-4T

Typical Deployment Use Cases

Small & mid-sized enterprise branch offices with hybrid MPLS/broadband connectivity
Multi-location retail, restaurant, and healthcare remote sites requiring integrated voice, security and WAN
Campus remote building edge routing with fiber uplink flexibility
Edge virtualization deployments consolidating network, security and UC functions
Secure remote worker VPN aggregation and direct internet breakout

Competitive Value Summary

The ISR4331/K9 delivers a cost-effective, space-saving all-in-one branch edge platform that eliminates separate firewall, WAN router, voice gateway and virtualization hardware. Its multi-plane architecture avoids performance bottlenecks when running concurrent routing, encryption and application services, making it a widely deployed legacy enterprise branch router for mixed voice-data-cloud workload environments.


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