Cisco ISR4431/K9 Integrated Services Router Platform for Enterprise WAN, 4000 Series Chassis | 1RU Rackmount | ISR 4431

Condition: Used; tested working. Minor cosmetic wear from prior installation possible. NO SFPs, or network modules besides what’s in the pictures. Includes: power cord, rack ears.

Product Description

The Cisco ISR4431 Integrated Services Router (ISR4431/K9) is an enterprise-grade branch/router platform designed to aggregate WAN connectivity, routing, security services, and voice/video readiness in a single chassis. It’s commonly deployed as a branch head-end for MPLS, broadband, or DIA circuits, and can be expanded with modular interface cards for additional WAN/LAN options. This unit is suited for networks that need stable routing, segmentation (VLAN/VRF), VPN capability, and consistent uptime in a 24/7 environment.

Markings Noted on Unit

• Model: ISR4431/K9 V04
• Assembly / PCB: 47-27185-01 Rev F0
• Country of manufacture: Made in Mexico
• Regulatory:
  • US: 5B11S01B0696
  • IC: 2461B-0950

Key Specifications (platform-level, module-dependent)

• Class: Enterprise Integrated Services Router (ISR 4000 Series)
• Use case: Branch WAN edge, VPN head-end (small/medium), segmentation and routing
• Modularity: Supports expansion via network interface modules (NIM) and service modules (slot availability depends on chassis revision/config)
• Management: Typically supports console management (RJ-45 and/or USB console depending on chassis configuration)
• Power: Internal power supply (exact PSU options depend on hardware revision)

If you want the listing to be ultra-accurate, include photos of the rear panel showing installed modules and port layout—ISR4431 capabilities vary based on what’s populated.

Features

• Enterprise routing platform suitable for branch/edge deployments
• Modular expansion for WAN/LAN interface flexibility (serial, additional Ethernet, etc., depending on modules)
• Designed to run network services beyond basic routing (feature availability depends on licensing/software image)
• Built for continuous operation in IT closets and telecom racks
• Commonly supports advanced features such as:
  • VLANs, static/dynamic routing (e.g., OSPF/BGP in many deployments)
  • QoS shaping/marking for voice/video and business apps
  • VPN capabilities (site-to-site and remote access, design dependent)
  • Network segmentation using VRF (design dependent)

Applications

• Branch office WAN router (primary or backup)
• MPLS / Metro-E / Internet edge routing and policy control
• VPN gateway for site-to-site connectivity
• Retail/restaurant chains needing standardized branch connectivity
• Industrial/warehouse routing where stable edge connectivity is required
• Lab/test environment for Cisco IOS XE routing/switching feature validation

Spheres of Application

• Corporate IT networks (branch + HQ)
• Managed service providers (CPE roles)
• Government/education branch networks
• Healthcare IT networks (infrastructure use—non-medical device function)

Serial / Identifier Decoding (best-effort)

• The “US: 5B11S01B0696” marking appears to be an identifier/serial-like code used for tracking and compliance.
• Many Cisco serial formats encode manufacturing site + date code + unit sequence, but the exact parsing can vary by generation and label format.
• Practical guidance for buyers: use this code for asset tracking and configuration inventory; for definitive manufacturing-date decoding, it typically requires Cisco’s internal serial format reference.

Cross-Referenced Models

• Cisco ISR 4000 family close relatives (same general platform class):
  • ISR4321/K9 (smaller branch class)
  • ISR4331/K9
  • ISR4351/K9
  • ISR4451/K9 (higher capacity class)

Comparable Products

• Juniper SRX branch/security gateways (comparable branch edge roles)
• Fortinet FortiGate appliances used as edge/router + security (role comparable, architecture different)
• HPE/Aruba edge gateways (deployment-dependent)
• Cisco Catalyst edge solutions (when edge routing is combined with switching, design dependent)

Use as Part of a Larger System

This router commonly sits inside a branch edge stack such as:

• ISP handoff → ISR4431 WAN interface → LAN switch (Catalyst/other) → endpoints/APs/VoIP
• Optional add-ons in the same design:
  • External firewall or UTM (or security handled on-router depending on configuration)
  • LTE/5G failover modem (architecture dependent)
  • Dual-WAN design (primary ISP + backup ISP) for resiliency
  • Site-to-site VPN to data center/cloud

Related

Cisco ISR 4431 router, enterprise branch router, WAN edge appliance, IOS XE router platform, modular network router, VPN gateway router, MPLS edge router, Gigabit Ethernet routing device, branch connectivity hardware, rackmount network router

Common Requests:

1. “Cisco ISR4431/K9 used tested working enterprise WAN router for branch office”
2. “ISR4431 router for site-to-site VPN and dual-WAN failover deployment”
3. “Replace ISR4331 with ISR4431—compatibility and migration considerations”
4. “ISR4431 modular NIM/SM slots—what modules fit and how to identify installed cards”
5. “Cisco ISR 4000 series router for lab environment IOS XE routing practice”

Trademarks Disclaimer

Cisco and all related product names are trademarks of their respective owners. Any references are used only to identify the product and to describe compatibility/comparison; no affiliation or endorsement is implied.

P125;HT3/5; GT00105