ISR4331/K9 – router – rack-mountable

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ISR4331/K9

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List Price: $3827 $463.29
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Weight 10.5 kg
Dimensions 56 × 55 × 17 cm
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ISR4331/K9 Description

The Cisco ISR4331/K9 Integrated Services Router, part of the Cisco 4000 Series, is designed for secure, high-performance branch deployments. Often referred to simply as ISR 4331 or Cisco 4331 router, it provides three Gigabit Ethernet ports (two combo RJ45/SFP and one RJ45), modular expansion through 2 NIM slots, and one SM-X slot for advanced services.Supporting 100 to 300 Mbps aggregate throughput (with Performance License upgrade), the ISR4331 is ideal for mid-sized branches requiring WAN aggregation, secure connectivity, and scalable performance. With up to 16 GB DRAM, integrated power options (AC or DC), and PoE support up to 250W, the platform delivers flexibility for branch networking and converged services.

Product Highlights

Aggregate Throughput (Default)
RJ-45-based ports
SFP-based ports

Front View

ISR4331-front

1

USB Type B mini port

2

Serial console port

3

AUX port

4

USB Type A port

5

Management port

6

LEDs

7

AC Power

 

 

Rear View

1

Double-wide NIM

2

NIMs

3

Removable module slot divider

4

SM-X slot

5

Ground connection

 

 

ISR4331-rear

Quick Specs

Parameter

Specification

Total Ports

3 × 10/100/1000 (2 RJ45/SFP combo + 1 RJ45)

NIM Slots

2

SM-X Slot

1

ISC Slot

1

Default DRAM

4 GB (up to 16 GB)

Default Flash

4 GB (up to 16 GB)

Aggregate Throughput

100 Mbps – 300 Mbps (licensed)

Power Supply

AC or DC; Max system power 250W with PoE, 530W total

Rack Units

1 RU

Key Features

Scalable Performance

Supports 100–300 Mbps aggregate throughput, ensuring that branch networks can start small and scale seamlessly as business traffic grows.

Flexible Modularity

Equipped with 2 NIM slots, 1 SM-X slot, and 1 ISC slot, the ISR4331 allows enterprises to integrate voice, security, storage, or WAN optimization services according to project needs.

Integrated Security

Provides advanced encryption, VPN, and firewall capabilities within the same platform, reducing the need for external security appliances and safeguarding critical enterprise data.

Optimized for Branch Deployments

Designed as a branch-edge and WAN aggregation router, ISR4331 delivers reliable connectivity for regional offices, supporting multi-service workloads and hybrid WAN strategies.

Unified Communication Readiness

Compatible with PVDM4 DSP modules, enabling voice, video, and conferencing integration for organizations adopting Cisco Unified Communications solutions.

Energy-Efficient & Compact

1RU rack-mount design with smart fan control and efficient PSU options, ensuring lower power consumption, reduced cooling needs, and space savings in branch racks.

Applications Scenarios

Branch Office WAN & Internet Gateway

Ideal for mid-sized branch offices requiring secure WAN aggregation, Internet access, and scalable bandwidth to support employees and cloud applications.

Financial & Retail Sectors

Widely adopted in banks, insurance firms, and retail chains where secure transactions, PCI compliance, and high reliability are crucial for business continuity.

Government, Healthcare & Education

Deployed in public sector, hospitals, and universities, the ISR4331 ensures protected data exchange, supports IP telephony, and enables converged services for critical operations.

Product Comparison

Feature

ISR4321/K9

ISR4331/K9

ISR4351/K9

GE Ports

2 (2 combo)

3 (2 combo + 1 RJ45)

3 (2 combo + 1 RJ45)

NIM Slots

2

2

3

SM-X Slot

–

1

1

ISC Slot

–

1

1

Default DRAM

4 GB

4 GB

4 GB

Max DRAM

8 GB

16 GB

16 GB

Default Flash

4 GB

4 GB

4 GB

Aggregate Throughput

50–100 Mbps

100–300 Mbps

200 Mbps – 400 Mbps

Max Power w/PoE

125W

250W

500W

Rack Units

1 RU

1 RU

2 RU

Weight

10.6 lb

12.25 lb

18.5 lb

ISR4331/K9 Supported Modules

Module Type / Part Numbers

Supported on ISR4331/K9

Network Interface Modules (NIMs)

Yes – 2 slots (single-wide or one double-wide)

NIM-1GE-CU-SFP / NIM-2GE-CU-SFP

Yes

NIM-1MFT-T1/E1 / NIM-2MFT-T1/E1

Yes

NIM-4MFT-T1/E1 / NIM-8MFT-T1/E1

Yes

NIM-1CE1T1-PRI / NIM-2CE1T1-PRI

Yes

NIM-8CE1T1-PRI

Yes

NIM-ES2-8 / NIM-ES2-8-P (EtherSwitch)

Yes (PoE requires PoE PSU)

NIM-SSD / NIM-HDD (Storage)

Yes

NIM LTE / xDSL variants

Yes (regional SKUs apply)

Service Modules (SM-X)

Yes – 1 slot for Enhanced Service Modules

SM-X-ES3-16-P / 24-P / 48-P

Yes

UCS-E compute/virtualization SM

Yes (depends on PSU/thermal capacity)

Packet Voice DSP (PVDM4)

Yes – 1 ISC slot on motherboard

PVDM4-32 / 64 / 128 / 256

Yes

Cisco UCS E-Series Server Modules

Not supported (only on ISR 4400 series)

Integrated PoE Daughter Card

Not supported on ISR4331 front GE ports

PoE via EtherSwitch NIMs/SM-X

Supported (requires PoE PSU)

Power Supply Options

AC PSU (default), DC PSU optional

Hot-Swap Dual PSU

Not supported on ISR4331

SFP Modules

Supported (100M/1G SFPs on combo ports)

Legacy WIC/EHWIC Cards

Not supported (only 4000-series NIM/SM-X)

Specifications

Parameter Specification Parameter Specification
Model Cisco ISR4331/K9 Series Cisco 4000 Series ISR
Ethernet Ports 3 × 10/100/1000 (2 × RJ45/SFP combo, 1 × RJ45) Management Port 1 × GE (dedicated)
NIM Slots 2 (single-wide or 1 double-wide with divider) SM-X Slot 1 Enhanced Service Module
ISC/PVDM4 Slot 1 slot for DSP modules USB Ports 1 × USB 2.0 Type-A, 1 × mini-USB console
Console Ports 1 × RJ-45 console, 1 × RJ-45 AUX OS Cisco IOS XE
Default DRAM 4 GB Maximum DRAM 16 GB
Default Flash 4 GB Maximum Flash 16 GB
Aggregate Throughput 100 Mbps (base), up to 300 Mbps (licensed) Encryption Throughput Up to 100 Mbps with services enabled
WAN/LAN Interfaces Provided via NIM/SM-X modules SFP Support 100/1000 Mbps SFPs, auto-media detection
Power Supply AC (default), optional DC PSU PoE Power Budget Up to 250W with PoE PSU
Max System Power 530W (with PoE) Hot-Swap PSU Not supported
Cooling Integrated fan system, smart speed control Operating Temp 0–40 °C (32–104 °F), up to 10,000 ft
Humidity (Operating) 10%–90% non-condensing Altitude -500 to 10,000 ft operating
Dimensions (H × W × D) 1.75 × 17.25 × 17.5 in (44 × 438 × 445 mm) Weight Approx. 12.25 lb (5.6 kg)
Rack Mount 1RU, 19-inch EIA/23-inch optional Compliance IEC/EN/UL 60950-1 & EN 62368-1, EMC CISPR22/24 Class A

Get More Information

Discover unbeatable prices and fast shipping for the ISR4331/K9 Access the detailed ISR4331/K9 datasheet and ensure you’re getting the best deal with our reliable delivery service. Need assistance? Our free live chat support is here to help. For more information about the product and pricing, contact us via Live chat or email us at [email protected]

Quality Certifications

Customer Reviews

Write A Review
5.0
(5 reviews)
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1 Stars
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    SysAdmin
    Posted on 02/09/2024
    Verified Buyer
    5.0

    Needed a replacement for a dead unit. Overnight shipping saved us.

    Luke Skywalker
    Posted on 05/08/2024
    Verified Buyer
    5.0

    An elegant weapon… I mean router, for a more civilized age. Works great.

    Han Solo
    Posted on 12/05/2024
    Verified Buyer
    5.0

    It made the Kessel Run… fast data transfer. Good kid, don’t get cocky.

    Branch IT
    Posted on 10/04/2024
    Verified Buyer
    5.0

    Classic branch router. We still deploy these for stability. Arrived new in box.

    Purchasing
    Posted on 22/12/2023
    Verified Buyer
    5.0

    Good price on the bundle. Shipping was consolidated with other items.

Questions & Answers

  • What does Cisco ISR4331/K9 deliver?

    A compact ISR 4000 router for small-to-mid branches, supporting modular WAN, IPsec VPN, CUBE, SRST, and optional SD-WAN with controller templates.

  • ISR4331 vs ISR4321—key differences?

    4331 provides higher throughput, more service capacity, and expansion options. Choose 4321 for smaller sites, 4331 for growing branches.

  • Is SD-WAN available?

    Yes. Migrate to Cisco SD-WAN to gain centralized policies and app-aware routing, or operate as a classic ISR.

  • Voice features?

    CUBE for SIP trunks, SRST for survivability, voice NIMs for analog, with QoS/LLQ to preserve call quality.

  • Resiliency design tips?

    Dual ISPs, LTE backup, and first-hop redundancy on LAN gateways. Validate failover behavior for voice and POS.

  • Management and automation?

    Web UI for quick start, then APIs/Ansible and telemetry for scale. Standardize templates to reduce drift.

  • Use cases?

    Retail branches, clinics, and regional offices consolidating WAN, security, and voice.

  • Licensing?

    Size SD-WAN, security, and CUBE licenses carefully; monitor actual consumption.

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Resources Downloads

  • ISR4331-K9 Datasheet

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