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The Cisco ISR4331 Series routers deliver a robust, integrated edge solution for small to midsize enterprise branch offices. As part of Cisco’s 4000 Family of Cisco Integrated Routers, the ISR4331 combines wired routing, SD-WAN, and on-box security services in a compact 1 RU platform.
Powered by Cisco IOS XE software and multicore architecture, these enterprise-grade routers support up to 300 Mbps of encrypted throughput, flexible modularity, and zero-touch provisioning—ideal for secure, high-performance WAN connectivity and value-added services at the branch.
Product Overview
Specification
| Specification | ISR4331/K9 (Base) | ISR4331-V/K9 (Voice UC Bundle) |
| Aggregate Throughput | 100 Mbps (default) up to 300 Mbps (performance license) | 100 Mbps (default) up to 300 Mbps (performance license) |
| CPU & DRAM | Multicore x86, 4 GB DRAM (up to 16 GB) | Multicore x86, 4 GB DRAM (up to 16 GB) |
| Flash Memory | 4 GB (up to 16 GB) | 4 GB (up to 16 GB) |
| Onboard Ports | 2× 1 GbE RJ-45, 2× 1 GbE SFP | 3× 10/100/1000 Mb/s RJ-45; 2× 1 GbE SFP |
| Module Slots | 2× NIM, 1× Enhanced SM-X, 1× Onboard ISC | 2× NIM, 1× Enhanced SM-X, 1× Onboard ISC |
| Voice DSP | — | PVDM4-32 digital signal processor for voice/video services |
| Security & SD-WAN | Cisco SD-WAN, IPsec, optional NGFW/IPS/AMP via bundles | Cisco SD-WAN, IPsec, NGFW/IPS/AMP included |
| Power Supply | 1× PWR-4330-AC internal, optional PoE converter | 1× PWR-4330-AC internal, optional PoE converter |
| Form Factor | 1 RU rack mount | 1 RU rack mount |
Core Features
-
High-Performance Multicore Architecture
Separates control, data, and services planes to maintain routing performance even when running multiple services. -
Flexible Modularity
Two NIM slots, one SM-X slot, and one onboard ISC slot support WAN interfaces, switching modules, and on-box compute or UC DSP modules (PVDM4-32 on the V bundle). -
Integrated SD-WAN & Security
Policy-driven overlay tunnels, zero-touch provisioning, and optional on-box NGFW, IPS, AMP, and URL Filtering streamline branch WAN and security consolidation. -
Pay-As-You-Grow Licensing
Base throughput of 100 Mbps with upgrade licenses to 300 Mbps; security and advanced routing features can be added as needed. -
Trustworthy Solutions
Secure Boot, hardware root of trust, and Secure Unique Device Identifier (SUDI) ensure platform integrity from manufacturing through runtime. -
Zero-Touch Provisioning
Cisco Plug and Play (PnP) and DNA Center integration enable automated deployment at scale, reducing branch setup time by up to 70%. -
IPsec VPN Acceleration
Hardware-accelerated cryptography delivers up to 300 Mbps of VPN throughput, supporting secure site-to-site and remote-access connectivity. -
Comprehensive Management
Manage via Cisco DNA Center, CLI, SNMP, REST APIs, or Embedded Event Manager for real-time monitoring, automation, and analytics
Competitor Comparison
| Feature | Cisco ISR4331 | FortiGate 60F | Juniper SRX300 |
| IPsec VPN Throughput | Up to 300 Mbps | 6.5 Gbps | 336 Mbps |
| Multicore Architecture | x86 multicore, 4 GB DRAM (16 GB max) | SoC plus SPU, 1 GB DRAM | Single CPU, 1 GB DRAM |
| Modularity | 2× NIM, 1× SM-X, 1× ISC | Fixed appliance | Fixed appliance |
| Embedded Security | NGFW, IPS, AMP, URLF (on-box) | NGFW, IPS, SD-WAN (hardware accelerated) | NGFW, IPS |
| SD-WAN Support | Cisco Catalyst SD-WAN | FortiOS Secure SD-WAN | Juniper Secure Connect |
| Form Factor | 1 RU rack mount | Desktop/appliance | Desktop |
Installation and Setup
Technical Guides
Site Survey & Placement
Assess WAN link types, rack space, and power. Plan NIM/SM-X module types (e.g., LTE, PoE, DSP) and ensure proper airflow clearance.
Core Allocation Modes
platform hardware multicore data-plane dedicates cores to packet forwarding. platform hardware multicore service-plane balances forwarding with container/UC workloads.
SD-WAN Configuration
sdwan
overlay name branch-overlay
exit
interface GigabitEthernet0/0/0
sdwan transport interface color biz-internet
no shutdown
Security Bundle Activation
license boot module isr4331 sec
security
ip inspect name NGFW tcp
url-filtering enable
malware-defense enable
exit
Module Installation (OIR)
hw-module subslot 0 power off
install module NIM-4G-LTE
hw-module subslot 0 power on
Software Upgrades
Use Cisco DNA Center or:
request platform software package install switch
Performance Monitoring
show platform hardware throughput level for forwarding performance
IP SLA probes for WAN latency and jitter
CLI Configuration Examples
Enable SD-WAN and Routing Features
configure terminal
sdwan
routing
exit
Create Overlay and VPN Profile
configure terminal
sdwan
overlay name branch-overlay
exit
crypto ikev2 proposal ike-prop
encryption aes-gcm
integrity sha256
exit
crypto ipsec profile ipsec-br
set ikev2 ipsec-prop ike-prop
exit
Configure WAN Interfaces
configure terminal
interface GigabitEthernet0/0/0
description Internet-Link
sdwan transport interface color biz-internet
no shutdown
exit
interface GigabitEthernet0/0/1
description MPLS-Link
sdwan transport interface color biz-mpls
no shutdown
exit
Apply IPsec Profile to Tunnel
configure terminal
interface Tunnel0
ip address 10.1.1.1 255.255.255.252
tunnel source GigabitEthernet0/0/0
tunnel mode ipsec ipv4
tunnel protection ipsec profile ipsec-br
exit
Enable NGFW and Security Policies
configure terminal
security ngfw
exit
configure terminal
policy-map type inspect SASE-POLICY
class type inspect HTTP
signature exception default
exit
Real Case Studies and Scenarios
-
Retail Branch Network
A national retailer deployed ISR4331/K9 at 200 locations. Zero-touch provisioning via Cisco DNA Center reduced rollout by 65%, and SD-WAN improved application performance across MPLS and broadband links. -
Unified Communications at a Campus
A university used ISR4331-V/K9 with PVDM4-32 modules to host Cisco UC services onsite. This converged branch infrastructure supported 500 concurrent voice/video channels with < 20 ms latency. -
Healthcare Multi-Site WAN
A healthcare system integrated ISR4331/K9 routers with on-box NGFW and URL filtering for HIPAA-compliant telemedicine. IPsec throughput of 250 Mbps ensured high-quality video consultations across sites.
Frequently Asked Questions (FAQs)
-
What is the default and maximum VPN throughput?
The ISR4331 provides a default of 100 Mbps and can be upgraded to 300 Mbps with a performance license. -
How many network ports are onboard?
The base ISR4331/K9 includes 2× 1 GbE RJ-45 and 2× 1 GbE SFP; the ISR4331-V/K9 voice bundle adds 3× 10/100/1000 Mb/s RJ-45 and 2× SFP ports. -
What expansion slots are available?
Both models feature 2 NIM slots, 1 Enhanced SM-X slot, and 1 onboard ISC slot for flexible WAN, switching, and compute modules. -
How much memory and storage can be installed?
Default 4 GB DRAM and 4 GB flash, expandable to 16 GB each for demanding services and logging . -
Does the ISR4331 support SD-WAN?
Yes—fully integrated Cisco Catalyst SD-WAN with policy-driven overlays and zero-touch provisioning is supported. -
What security services are available on-box?
Optional on-box NGFW, Snort IPS, Advanced Malware Protection (AMP), and URL Filtering through security bundles. -
How can the router be managed?
Manage via Cisco DNA Center, CLI, SNMP, REST APIs, or Embedded Event Manager for comprehensive automation and visibility.
Conclusion
The Cisco ISR4331 Series routers offer a versatile, enterprise-grade wired router platform, combining SD-WAN, advanced security, and modular flexibility in a compact 1 RU form factor.
With pay-as-you-grow throughput, multicore performance, and optional voice and UC integration, the ISR4331 scales to meet the evolving needs of modern branch offices.
Its integration with Cisco DNA Center and zero-touch provisioning accelerates deployment, reduces operational costs, and ensures consistent policy and security enforcement across distributed sites.
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