ISR4331/K9 – 3x1G Ports (2 RJ45, 2 SFP) – 2 NIM + 1 SM-X Slots – ISR 4331 Branch Router

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ISR4331/K9 Description

The ISR4331/K9 is a Cisco ISR 4331 integrated services router from the Cisco 4000 Family for branch offices that combine WAN routing, voice and a service module in a 1RU chassis. The router has three onboard Gigabit Ethernet ports, two NIM slots, one SM-X slot, an ISC voice DSP slot and 4 GB of DRAM, with 100 Mbps of aggregate throughput by default or 300 Mbps under a performance license. Without the HSEC license, encryption stops at 1,000 secure tunnels and 250 Mbps of crypto bandwidth.

Quick Specs

Parameter

Specification

Onboard WAN or LAN ports

3 x 10/100/1000; 2 RJ-45-based and 2 SFP-based

Management port

1 dedicated Gigabit Ethernet port

Module slots

2 NIM slots, 1 enhanced SM-X slot and 1 onboard ISC slot

Aggregate throughput

100 Mbps default; 300 Mbps with FL-4330-PERF-K9

DRAM

4 GB, upgradable to 16 GB

Default flash

4 GB, upgradable to 16 GB

Default power supply model

PWR-4330-AC internal AC supply; 250W maximum system power

Default PoE budget

None; the default AC supply carries no PoE

PoE with PWR-4330-POE-AC

250W for endpoints, 530W platform maximum

Redundant power supply

Not available

Software modes

Autonomous or Catalyst SD-WAN controller mode on one universalk9 image from Cisco IOS XE 17.2.1

Encryption without HSEC

1,000 secure tunnels and 250 Mbps of crypto bandwidth

Form factor

1RU, 1.75 x 17.25 x 17.25 in; rack or wall mount

Product Performance

Aggregate Throughput (Default)
Aggregate Throughput (Performance License)
Enhanced Service Module Slot

Key Features

A Service Module Slot In 1RU

The SM-X slot links to the system at up to 10 Gbps and to the other module slots at 1 Gbps. SM-X-6X1G, for example, adds six routed dual-mode GE/SFP ports to the chassis without taking a NIM slot.

Third NIM Through A Carrier Card

When the design calls for more NIMs than service modules, an optional carrier card converts the SM-X slot into a NIM slot. A console server built on NIM-24A asynchronous modules then holds three of them, 72 serial lines in one chassis.

Throughput Set By License

As shipped, the router forwards 100 Mbps of aggregate traffic. A performance-on-demand license delivered remotely triples that to 300 Mbps on the same hardware, and a separate boost license covers CEF-only forwarding over the onboard ports.

Routing Or SD-WAN On One Image

From Cisco IOS XE 17.2.1 the universalk9 image runs the router either in autonomous mode or under Catalyst SD-WAN controllers. Autonomous mode keeps a perpetual license; controller mode uses a term license that must be renewed.

PoE For Integrated Switch Modules

The PoE version of the internal supply sends 802.3af or 802.3at power to integrated switch modules, up to 250W for endpoints. Eight 30W PoE+ endpoints would draw 240W, inside that limit.

Rack Or Wall Installation

The chassis is 1RU high and 17.25 in deep, ships with 19-inch rack brackets and can also be mounted on a wall. Typical sound pressure is 52.8 dBA, with air moving from the I/O side to the bezel side.

Application Scenarios

Branch WAN Edge With Mixed Circuits

A branch office with a fiber circuit from one carrier and copper broadband from another terminates both on the router’s onboard Gigabit ports, and the router handles routing, zone-based firewall and IPsec VPN once the security package is licensed.

Catalyst SD-WAN Branch Site

In a Catalyst SD-WAN deployment, the router joins the overlay in controller mode and forwards branch traffic across the transport circuits under policies pushed from the central controllers.

Branch Voice Gateway And SIP Trunk

Offices that keep a local call path use the router as a voice gateway, with CUBE connecting the call controller to a carrier SIP trunk and SRST keeping phones working during a WAN outage. A PVDM4 in the ISC slot supplies the DSP resources for transcoding and conferencing.

Product Comparison

Parameter

ISR4331/K9

ISR4321/K9

ISR4351/K9

C8200-1N-4T

Total onboard WAN or LAN 1G ports

3 (2 RJ-45-based, 2 SFP-based)

2 (2 RJ-45-based, 1 SFP-based)

3 (3 RJ-45-based, 3 SFP-based)

4 (2 RJ-45, 2 SFP)

Aggregate throughput (default)

100 Mbps

50 Mbps

200 Mbps

Not published

Aggregate throughput (performance license)

300 Mbps

100 Mbps

400 Mbps

Not published

IPsec throughput (1400 bytes)

Not published

Not published

Not published

Up to 1 Gbps

Module slots

2 NIM, 1 SM-X, 1 ISC

2 NIM, 1 ISC

3 NIM, 2 SM-X, 1 ISC

1 NIM, 1 PIM

DRAM

4 GB (16 GB maximum)

4 GB (8 GB maximum)

4 GB (16 GB maximum)

8 GB (32 GB maximum)

Default power supply

Internal AC, 250W maximum system power

External AC, 125W maximum system power

Internal AC, 430W maximum system power

PWR-CC1-100WAC 100W AC, integrated

Default PoE budget

0W

0W

0W

0W

Maximum endpoint PoE

250W with PWR-4330-POE-AC

120W with PWR-4320-POE-AC

500W with PoE power supply

150W with PWR-CC1-150WAC

ISR4331/K9 and ISR4351/K9 share three onboard Gigabit ports, but ISR4331/K9 carries two NIM slots and one SM-X slot against three and two, and licenses up to 300 Mbps against 400 Mbps. A branch that needs more than 300 Mbps, a third NIM alongside a service module, or more than 250W of endpoint PoE moves to ISR4351/K9. ISR4321/K9 drops the SM-X slot and the third port and stops at 100 Mbps, which suits sites with no service module and no more than 120W of PoE. C8200-1N-4T brings four onboard ports, 8 GB of DRAM and up to 1 Gbps of IPsec, but only one NIM slot plus a PIM slot. Sites on DC power need ISR4331-DC/K9, which accepts 24 to 60 VDC and supports no PoE.

Ordering Checklist

  • Technology package: The base router runs IP Base only; add SL-4330-SEC-K9 for IPsec and zone-based firewall, SL-4330-UC-K9 for CME, SRST and CUBE, or SL-4330-APP-K9 for MPLS and AVC.
  • HSEC license: Add FL-4330-HSEC-K9 when the design needs more than 1,000 secure tunnels or more than 250 Mbps of crypto bandwidth. The license requires the security package and has no evaluation period.
  • Performance license: Order FL-4330-PERF-K9 when the branch needs more than 100 Mbps of aggregate throughput. The license raises the ceiling to 300 Mbps; without it the router stays at 100 Mbps.
  • Memory and flash: MEM-4300-4GU8G or MEM-4300-4GU16G takes DRAM from 4 GB to 8 GB or 16 GB, and MEM-FLSH-4U8G or MEM-FLSH-4U16G takes flash from 4 GB to 8 GB or 16 GB.
  • PoE power supply: Order PWR-4330-POE-AC when integrated switch modules must power endpoints. The standard AC supply delivers no PoE.
  • Mounting kit: 19-inch rack brackets ship with the router; add ACS-4330-RM-23= for a 23-inch rack or ACS-4330-WM= for wall installation.

Optional Add-ons

Model

Description

PWR-4330-POE-AC

AC power supply with PoE for the ISR 4330; up to 250W of endpoint PoE

PWR-4330-AC

AC power supply for the ISR 4330

MEM-4300-4GU8G

DRAM upgrade from 4 GB to 8 GB (4G+4G) for the ISR 4330 and ISR 4350

MEM-4300-4GU16G

DRAM upgrade from 4 GB to 16 GB (8G+8G) for the ISR 4330 and ISR 4350

MEM-FLSH-4U8G

eUSB flash upgrade from 4 GB to 8 GB for the ISR 4300

MEM-FLSH-4U16G

eUSB flash upgrade from 4 GB to 16 GB for the ISR 4350 and ISR 4330

FL-4330-PERF-K9

Performance license raising aggregate throughput from 100 Mbps to 300 Mbps

FL-4330-BOOST-K9

Boost performance license for CEF-only forwarding on the ISR 4330

FL-4330-HSEC-K9

HSEC export compliance license for the ISR 4330

SL-4330-SEC-K9

Security technology package license

SL-4330-UC-K9

Unified Communications technology package license

SL-4330-APP-K9

Application Experience technology package license

PVDM4-32

32-channel voice DSP module for the onboard ISC slot

PVDM4-64

64-channel voice DSP module for the onboard ISC slot

SM-X-6X1G

6-port dual-mode GE/SFP service module for the SM-X slot

NIM-24A

24-port asynchronous serial NIM

ACS-4330-RM-23=

23-inch rack kit for the ISR 4330

ACS-4330-WM=

Wall mount kit for the ISR 4330

ACS-4330-FANASSY=

Fan assembly for the ISR 4330

Front View

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

 

 

Specifications

Parameter Specification Parameter Specification
Product ID ISR4331/K9 Rack height 1RU
Total onboard WAN or LAN 10/100/1000 ports 3 RJ-45-based ports 2
SFP-based ports 2 Total onboard WAN or LAN 10Gbps ports 0
Dual-mode port behavior An SFP port shares the physical port of the same-numbered RJ-45 port; one medium at a time RJ-45 port standards 10BASE-T, 100BASE-TX, 1000BASE-T
SFP port modules 1000BASE-LX/LH, SX, ZX, CWDM and 100 Mbps SFP modules Management port 1 dedicated Gigabit Ethernet port
NIM slots 2, with a removable slot divider for a double-wide NIM Enhanced service-module slots 1
Double-wide service-module slots 0 Onboard ISC slot 1, for PVDM4 voice DSP modules
OIR (all I/O modules) Yes Aggregate throughput (default) 100 Mbps
Aggregate throughput (performance license) 300 Mbps with FL-4330-PERF-K9 Default memory DRAM 4 GB
Maximum memory DRAM 16 GB Flash 4 GB
Maximum flash memory 16 GB External USB 2.0 slots (type A) 1
USB console port (type B mini) 1 Serial console port (RJ-45) 1
Serial auxiliary port (RJ-45) 1 Power-supply options Internal AC and PoE
Default power supply model PWR-4330-AC, internal AC Default PoE budget None; the default AC supply carries no PoE
Redundant power supply Not available AC input voltage 100 to 240 VAC autoranging
AC input frequency 47 to 63 Hz AC input current range 3 to 1.3 A
Typical power (no modules) 42W Maximum power with AC power supply 250W
Maximum power with PoE power supply (platform only) 530W Maximum endpoint PoE power from PoE power supply 250W
PoE standards from the PoE power supply 802.3af PoE and 802.3at PoE+ to integrated switch modules Dimensions (H x W x D) 1.75 x 17.25 x 17.25 in (44.45 x 438.15 x 438.15 mm)
Rack-mount 19 in. EIA Included Rack-mount 23 in. EIA Optional
Wall-mount Supported Weight with AC PS (no modules) 6.2 kg (13.5 lb)
Weight with AC PS with PoE 6.4 kg (14.1 lb) Typical weight (fully loaded with modules) 7.3 kg (16.1 lb)
Airflow I/O side to bezel side MTBF 587,250 hours
Operating temperature 0°C to 40°C (32°F to 104°F) Storage temperature -40°C to 70°C (-40°F to 158°F)
Relative humidity 5% to 85% operating; 5% to 95% nonoperating Operating altitude 0 to 3,050 m (10,000 ft); 0 to 2,000 m (6,560 ft) in China
Sound pressure (typical/maximum) 52.8/74.8 dBA Sound power (typical/maximum) 61.2/81.6 dBA
Safety certifications UL 60950-1, CAN/CSA C22.2 No. 60950-1, EN 60950-1, AS/NZS 60950-1, IEC 60950-1 EMC certifications ICES-003 Class A, EN55032 Class A, CISPR32 Class A, AS/NZS CISPR 32 Class A, VCCI V-3, CNS 13438, EN 300-386, EN 55024, CISPR 24
Software image universalk9; autonomous and Catalyst SD-WAN controller mode from Cisco IOS XE 17.2.1 Technology packages IP Base by default; Security, Unified Communications and Application Experience by license
Crypto limits without HSEC 1,000 secure tunnels and 250 Mbps of crypto bandwidth

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Quality Certifications

Customer Reviews

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    Evelyn Ford
    Posted on 29/04/2026
    Verified Buyer
    4.0

    We stretched our hardware budget further than we thought possible. Invoice formatting was a bit different from what our AP system expects, but workable.

    Frank Thompson
    Posted on 20/12/2025
    Verified Buyer
    5.0

    We’ve placed orders for multiple projects now. Same great experience each time.

    Hannah Green
    Posted on 17/12/2025
    Verified Buyer
    5.0

    We finished the install ahead of schedule. The product cooperated fully.

    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.

Questions & Answers

  • Which ROMMON release does ISR4331/K9 need for IOS XE 16.12 and for IOS XE 17.6?

    ISR4331/K9 needs ROMMON 16.7(3r) for IOS XE 16.3.x through 16.12.x, and ROMMON 16.12(2r) for IOS XE 17.1.x through 17.6.x, per the Cisco ISR 4000 software installation guide. IOS XE 16.3.x is the earliest train shown for this router.
  • How many NIM-16A or NIM-24A modules can ISR4331/K9 hold?

    ISR4331/K9 takes up to 2 asynchronous serial NIMs, either NIM-16A or NIM-24A, in its NIM slots. With an SM-X-NIM-ADPTR carrier installed in the service-module slot, the router takes a third asynchronous module for more console ports.
  • Can ISR4331/K9 run from a DC power supply?

    No. ISR4331/K9 uses an internal AC supply or the PoE supply. DC power is sold as the separate ISR4331-DC/K9, which takes a 24 to 60 V DC input, draws up to 250 W and carries no PoE. That DC version also lists a short-term operating temperature of 0 to 55 C under NEBS GR-63-CORE, per the Cisco ISR 4000 data sheet.
  • Which connections does each NIM slot on ISR4331/K9 offer?

    Each NIM slot on ISR4331/K9 offers up to two 2 Gbps connections, one to the route processor and one for direct module-to-module traffic. The onboard ISC slot for PVDM4 voice DSP modules uses its own link of up to 2 Gbps to the route processor.
  • Which rack kits and spare parts are listed for ISR4331/K9?

    ACS-4330-RM-19= is the 19-inch rack kit and ACS-4330-RM-23= the 23-inch rack kit for ISR4331/K9. ACS-4330-WM= is the wall mount kit and ACS-4330-FANASSY= the fan assembly spare, per the Cisco ISR 4330 spares listing.

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