Cisco ISR4431/K9
Cisco ISR 4431 (4GE,3NIM,8G FLASH,4G DRAM)
Product Highlights
What's Included
4GB DRAM Control/Services Plane (2x MEM-4400-2G)
8GB Flash (1x MEM-FLSH-8G)
(1) PWR-4430-AC
(1) AC Power Cord
(1) Rackmount Kit (ACS-4430-RM-19)
Enterprise branch offices demand routers that can keep pace with growing application workloads, secure distributed traffic, and adapt to new services — all without costly hardware replacements. The Cisco ISR 4431 (ISR4431/K9) is a member of the Cisco 4000 Series Integrated Services Router family, purpose-built for branch and WAN edge deployments that require high throughput, modular expansion, and software-defined flexibility.
The ISR 4431 delivers 500 Mbps to 1 Gbps of aggregate throughput (expandable via performance licensing) across four onboard Gigabit Ethernet interfaces (4 RJ-45 and 4 SFP ports). Its three Network Interface Module (NIM) slots and one Integrated Services Card (ISC) slot allow IT teams to add WAN connectivity, voice gateways, switching, wireless LAN controllers, or 4G LTE modules as requirements change — protecting the initial investment.
Powered by Cisco IOS XE with a distributed multicore architecture that separates the data plane from the control and services planes, the ISR 4431 maintains consistent forwarding performance even as security, voice, and WAN optimization services are activated. Embedded IPsec VPN hardware acceleration, support for Cisco SD-WAN, and compatibility with Cisco DNA Center make this router an ideal foundation for intent-based networking at the branch. Shipped in a compact 1RU form factor with dual power supply support, the ISR4431/K9 balances enterprise-grade capability with operational simplicity.
Features & Benefits
License-Based Performance Scaling
The ISR 4431 ships with a 500 Mbps default throughput tier and can be upgraded to 1 Gbps with the FL-44-PERF-K9 performance license — no hardware swap required. A Boost license unlocks the full forwarding capacity of the hardware. This pay-as-you-grow model lets organizations match router performance to actual WAN bandwidth, avoiding over-provisioning costs.
Modular Expansion via NIM & ISC Slots
Three NIM slots and one ISC slot accept a wide range of Cisco modules — T1/E1 voice interfaces, LTE wireless WAN cards, Ethernet switching modules, and more. Online Insertion and Removal (OIR) support means modules can be hot-swapped without disrupting other services, minimizing maintenance windows.
Distributed Multicore Architecture
The ISR 4431 uses separate CPU resources for the data plane and the control/services plane. This architecture ensures that enabling security, voice, or WAN optimization features does not degrade forwarding performance. The data plane leverages an emulated Flow Processor for ASIC-like packet handling efficiency.
Embedded Security & VPN Acceleration
Built-in IPsec VPN hardware acceleration offloads encryption and decryption from the CPU, enabling high-throughput site-to-site and remote-access VPN tunnels. With an optional Security license, the ISR 4431 adds zone-based firewall, DMVPN, FlexVPN, and EZVPN capabilities — consolidating branch security into a single device.
Cisco SD-WAN & DNA Ready
The ISR 4431 supports Cisco SD-WAN (formerly Viptela) and integrates with Cisco DNA Center for centralized policy management, analytics, and automation. This makes it a strong candidate for organizations transitioning from traditional WAN to an intent-based, software-defined architecture.
Deployment Scenarios
Enterprise Branch Office WAN Edge
Deploy the ISR 4431 as the primary WAN edge router at medium-to-large branch offices. Its 500 Mbps–1 Gbps throughput handles typical branch traffic loads, while NIM expansion supports T1/E1 backup links, 4G LTE failover, or direct fiber uplinks via SFP.
Secure SD-WAN Hub or Spoke
Use the ISR 4431 as a spoke or regional hub in a Cisco SD-WAN fabric. Embedded IPsec acceleration and IOS XE support for Catalyst SD-WAN enable encrypted overlay tunnels across MPLS, broadband, and LTE transports with centralized policy orchestration.
Unified Communications Branch Gateway
With a UC license and voice NIM modules, the ISR 4431 serves as a Cisco Unified Communications Manager Express (CME) or Survivable Remote Site Telephony (SRST) gateway, providing local call processing and PSTN breakout at remote sites.
Managed Service Provider CPE
Service providers can deploy the ISR 4431 as customer-premises equipment for managed WAN, security, and voice services. License-based throughput tiers and modular interfaces simplify service tiering and future upgrades without truck rolls.
General
Performance
Interfaces & Expansion
Memory & Storage
Power
Physical
Environmental
Compliance
Compatibility Notes
Compatible NIM Modules (examples): NIM-1MFT-T1/E1, NIM-2MFT-T1/E1, NIM-1GE-CU-SFP, NIM-2GE-CU-SFP, NIM-4G-LTE-NA, NIM-ES2-4, NIM-ES2-8, NIM-SSD.
Performance Licenses: FL-44-PERF-K9 (1 Gbps performance tier), FL-44-BOOST-K9 (Boost tier — unlocks full hardware throughput).
Software Licenses: SL-44-IPB-K9 (IP Base), SL-44-SEC-K9 (Security), SL-44-UC-K9 (Unified Communications), L-SL-44-APP-K9= (AppX/WAAS).
Operating System: Cisco IOS XE. Last supported release trains for this platform are 17.9.x and 17.12.x.
Power Supply: Ships with PWR-4430-AC. Optional PWR-4430-DC and PWR-4430-POE-AC available separately.
Rackmount Kit: Included ACS-4430-RM-19 supports standard 19-inch racks.
Downloads & Resources
Frequently Asked Questions
| Part Number | Product | Key Difference |
|---|---|---|
| ISR4351/K9 | Cisco ISR 4351 | Lower throughput tier (200–400 Mbps default) with 3 NIM + 2 SM-X slots; suits smaller branches with service module needs. |
| ISR4451-X/K9 | Cisco ISR 4451-X | Higher throughput (1–2 Gbps default) with 3 NIM + 2 SM-X slots; designed for larger branch or regional hub deployments. |
| ISR4431-SEC/K9 | Cisco ISR 4431 Security Bundle | Same ISR 4431 hardware but ships with the Advanced Security license pre-installed (zone-based firewall, IPsec VPN, DMVPN). |
| C8300-1N1S-4T2X | Cisco Catalyst 8300 Series Edge | Cisco's recommended next-generation replacement for the ISR 4431; Catalyst 8000 platform with enhanced SD-WAN and cloud integration. |
