ISR4351/K9 – router – rack-mountable

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ISR4351/K9

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List Price: $3827 $699
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ISR4351/K9 Description

Cisco ISR4351/K9 (also called ISR 4351 or Cisco 4351 router) is a high‑performance branch router in the Cisco 4000 Series. It features three Gigabit Ethernet ports (two combo RJ‑45/SFP and one RJ‑45), three NIM slots, and one SM‑X service‑module slot to consolidate WAN, voice, security, and application services on a single platform. With 200–400 Mbps aggregate throughput (via performance licensing), up to 16 GB DRAM, and 500 W PoE capacity through supported EtherSwitch modules, ISR4351 is ideal for mid‑to‑large branches that need scalable WAN performance, unified communications, and on‑box service flexibility.

Product Highlights

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

Quick Specs

Parameter

Specification

GE Ports

3 × 10/100/1000 (2 × RJ‑45/SFP combo + 1 × RJ‑45)

NIM Slots

3

SM‑X Slot

1

ISC (PVDM4)

1

Aggregate Throughput

200–400 Mbps (licensed)

Default / Max DRAM

4 GB / 16 GB

Default / Max Flash

4 GB / 16 GB

Max Power with PoE

500 W

Rack Units

2 RU

Weight

~18.5 lb (8.4 kg)

Key Features

Scalable Branch Performance

Delivers 200–400 Mbps aggregate throughput, ensuring smooth growth for branch WAN, VPN, and cloud workloads without forklift upgrades.

Rich Modularity

Supports 3× NIM and 1× SM-X slots, enabling integration of WAN optimization, security, LTE/xDSL, or switching modules tailored to diverse branch requirements.

Advanced Unified Communications

With PVDM4 DSPs and voice NIMs, it provides SRST, conferencing, and transcoding, ensuring branch survivability and high-quality voice services.

Integrated Security

Offers hardware-accelerated VPN and policy-based segmentation, essential for hybrid cloud, SD-WAN, and compliance-driven industries.

High PoE Capacity

Up to 500 W PoE budget when combined with PoE-capable EtherSwitch NIM/SM-X modules, allowing direct powering of IP phones, wireless access points, and surveillance cameras.

Enterprise-Grade Reliability

Built with field-replaceable PSUs, robust thermal management, and Cisco IOS XE software for long-term, stable branch operations.

Applications Scenarios

Enterprise & Multinational Branch Networks

ISR4351 is ideal for medium to large branch offices that need secure WAN aggregation, application visibility, and integrated collaboration services.

Financial, Retail, and Service Provider Environments

Delivers high-availability WAN, encrypted VPN, and multi-service aggregation for industries where uptime, compliance, and secure transactions are critical.

Public Sector, Healthcare, and Education Campuses

Enables converged services, such as secure inter-site connectivity, IP telephony, and IoT device integration, within regulated and mission-critical environments.

Front View

ISR4351/K9

1

Power supply unit

2

Router fan tray (hidden behind the removable bezel)

3

LEDs

4

Router power On/Off switch

Rear View

1

Enhanced Service Module (SM-X) slot

2

Enhanced Service Module (SM-X) slot

3

Ground connection

4

NIM slots

5

GE management port

6

USB Type A port

7

USB Type B mini port

8

Auxiliary port

9

Console port

10

RJ-45 port (GE 0/0/0, GE 0/0/1)

11

SFP port (GE 0/0/0, GE 0/0/1, GE 0/0/2)

12

RJ-45 port (GE/0/0/2)

ISR4351/K9

Product Comparison

Feature

ISR4321/K9

ISR4331/K9

ISR4351/K9

GE Ports

2 (2 combo)

3 (2 combo + 1 RJ‑45)

3 (2 combo + 1 RJ‑45)

NIM Slots

2

2

3

SM‑X Slot

–

1

1

ISC (PVDM4)

–

1

1

Default / Max DRAM

4 GB / 8 GB

4 GB / 16 GB

4 GB / 16 GB

Default / Max Flash

4 GB / 8–16 GB

4 GB / 16 GB

4 GB / 16 GB

Aggregate Throughput

50–100 Mbps

100–300 Mbps

200–400 Mbps

Max Power with PoE

125 W

250 W

500 W

Rack Units

1 RU

1 RU

2 RU

Weight

~10.6 lb

~12.25 lb

~18.5 lb

Voice DSP (PVDM4)

Supported via NIM

Supported

Supported

PoE Availability

Via EtherSwitch NIM + PoE PSU

EtherSwitch NIM/SM‑X + PoE PSU

EtherSwitch NIM/SM‑X + PoE PSU

ISR4351/K9 Supported Modules

Module Type / Part Numbers

Supported on ISR4351/K9

Network Interface Modules (NIMs)

Yes – 3 slots (single-wide; double-wide supported with divider removed)

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-capable 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 (subject to PSU/thermal capacity)

Packet Voice DSP (PVDM4)

Yes – 1 ISC bay 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 built-in GE ports

PoE via EtherSwitch NIMs/SM-X

Supported (up to 500 W with PoE PSU)

Power Supply Options

AC PSU (default), DC PSU optional

Hot-Swap Dual PSU

Not supported on ISR4351

SFP Modules

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

Legacy WIC/EHWIC Cards

Not supported (4000-Series uses only NIM/SM-X)

Specifications

Parameter Specification Parameter Specification
Model ISR4351 (Cisco 4000 Series ISR) Form Factor 2RU rack-mount
GE Data Ports 3 × 10/100/1000 (2 × RJ‑45/SFP combo + 1 × RJ‑45) Dedicated Mgmt Integrated management via front-panel GE
NIM Slots 3 (single‑wide; double‑wide supported per divider) SM‑X Slot 1 (Enhanced Service Module)
ISC / PVDM4 1 ISC bay for PVDM4 DSP modules USB Ports USB 2.0 Type‑A (storage), mini‑USB console
Console / AUX RJ‑45 console and RJ‑45 auxiliary OS Cisco IOS XE
Default / Max DRAM 4 GB / 16 GB Default / Max Flash 4 GB / 16 GB
Aggregate Throughput 200–400 Mbps (licensed) Encryption Capability Hardware‑accelerated (license dependent)
WAN/LAN via Modules Provided through NIM/SM‑X (T1/E1, Serial, xDSL, LTE, L2/L3 Switch) SFP Support 100/1000‑Mb SFPs on combo ports
Power Supply AC PSU (default); DC PSU option Max PoE Budget Up to 500 W with PoE‑capable PSU & modules
Cooling Integrated fans with smart control Operating Temp 0–40 °C (32–104 °F)
Operating Humidity 10%–90% non‑condensing Altitude (Operating) ‑500 to 10,000 ft
Dimensions (HxWxD) ~3.5 × 17.25 × 17.5 in (2RU height) Weight ~18.5 lb (8.4 kg)
Compliance Safety: IEC/EN/UL 60950‑1/62368‑1; EMC: CISPR 22/24 Class A (region dependent) Mounting 19‑inch EIA rack; optional accessories available
Licensing Performance, Security, UC, AppX (Smart Licensing) Typical Roles Branch WAN/Internet gateway, UC gateway, converged services

Get More Information

Discover unbeatable prices and fast shipping for the ISR4351/K9 Access the detailed ISR4351/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
(4 reviews)
5 Stars
4
4 Stars
0
3 Stars
0
2 Stars
0
1 Stars
0
    Leia Organa
    Posted on 15/07/2024
    Verified Buyer
    5.0

    Hope is not a strategy, good hardware is. This router is reliable.

    Network Eng
    Posted on 05/03/2024
    Verified Buyer
    5.0

    3 GE ports and SM slots give us room to grow. Voice modules work perfectly.

    Procurement
    Posted on 20/01/2024
    Verified Buyer
    5.0

    German customs clearance went well. Invoice correct.

    Chewbacca
    Posted on 08/11/2023
    Verified Buyer
    5.0

    (Wookiee noises of approval) – Strong box. Good router.

Questions & Answers

  • What is ISR4351/K9 designed for?

    A versatile ISR 4000 for mid-size branches, offering modular WAN, decent crypto throughput, and support for CUBE, SRST, and SD-WAN in a cost-effective footprint.

  • ISR4351 vs ISR4331—how to choose?

    4351 provides more CPU and slots for services. Choose 4331 for smaller branches; 4351 when you need more VPN or voice scale.

  • Is SD-WAN supported?

    Yes. Runs IOS XE in SD-WAN mode with policy-based path selection and controller-driven templates, or as a traditional ISR.

  • What voice options exist?

    CUBE for SIP trunks, SRST for local dial tone, and NIMs for FXS/FXO/PRI integration. Apply QoS and policing to protect calls.

  • How to ensure uptime?

    Deploy dual links, LTE backup, and HSRP/VRRP toward LAN. Test failover during business-as-usual traffic.

  • How to manage at scale?

    Use APIs/NETCONF, Ansible, and telemetry for automation and visibility. Maintain golden images and staged upgrades.

  • Common use cases?

    Healthcare clinics, education sites, and retail HQ branches with moderate traffic and voice requirements.

  • Licensing guidance?

    Right-size SD-WAN, security, and CUBE sessions to expected loads; revisit as usage grows.

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