Cisco ISR4321-FAN (ACS-4320-FANASSY=) Full English Description

Product Overview

Important Hardware Note:ISR4321 fan tray is NOT hot-swappable (OIR unsupported). The router must be powered down before fan tray removal. Extended operation without the fan assembly will trigger thermal protection and permanent hardware risk. Strict ESD anti-static procedures are required for maintenance. This fan tray cannot be interchanged with ISR4331, ISR4351, ISR4400 series or any other Cisco ISR / ASR router fan assemblies. Standard airflow direction is Front-to-Rear (bezel intake, rear port exhaust). Reverse airflow variants are not available for ISR4321.

Key Features

1. Intelligent Variable-Speed Thermal Regulation

   The fan assembly dynamically adjusts fan rotational speed based on real-time internal chassis temperature and ambient operating altitude. Fans run at low RPM under light workloads to minimize power consumption and acoustic noise, and automatically ramp up speed to increase airflow when internal temperatures rise. All thermal metrics are monitored and reported via Cisco IOS XE.
2. Front-to-Rear Airflow Architecture

   Cool air enters the chassis from the front bezel side; heated air exhausts toward the rear I/O port side. Maintain unobstructed ventilation space on both front and rear rack sides to avoid airflow restrictions and thermal hotspots.
3. Maintenance Requirement

   Power must be fully removed from ISR4321 before fan tray replacement. Do not remove the fan tray while the router is powered on. After installation, IOS XE automatically detects and validates fan hardware status upon boot-up.
4. System Monitoring & Alarm Notification

   IOS XE continuously monitors the RPM status of each individual fan rotor.

• Green Status LED: All fan rotors operate normally within rated speed range
• Amber LED: Single fan rotor failure detected
• Blinking Amber LED: Multiple fan faults or fan tray missing
  The system outputs console syslog messages and SNMP traps to notify administrators once fan anomalies are detected.

1. Internal Fan Redundancy

   Multiple independent fan rotors are built into one tray assembly. If a single rotor fails, remaining fans deliver limited temporary cooling capacity. Network engineers should arrange immediate FRU replacement upon receiving fan fault alerts to prevent overheating outages.
2. Enterprise-Grade Reliability

   Industrial brushless DC fans engineered for 24/7 continuous operation in enterprise branch offices, SD-WAN edge sites, remote retail locations and unified communications voice gateway deployments.

Supported Hardware Platforms

• Cisco ISR4321/K9 Integrated Services Router

Not compatible: ISR4331, ISR4351, ISR4431, ISR4451-X, ISR3900/3800 legacy ISR, ASR aggregation routers, Catalyst / Nexus switching hardware.

Typical Application Scenarios

• Enterprise branch SD-WAN, internet access and voice gateway deployments running IOS XE on ISR4321 routers
• Spare replacement cooling fan tray for existing ISR4321 router maintenance
• Distributed branch network infrastructure refresh and hardware failure replacement

Technical Specifications

• Form Factor: Integrated front fan tray assembly
• Official Spare PN: ACS-4320-FANASSY= (market alias: ISR4321-FAN)
• Airflow Direction: Front-to-Rear (standard only)
• Hot Swappable (OIR):Not Supported
• Monitoring: Per-fan RPM monitoring, front-panel status LED, IOS XE syslog & SNMP trap support
• Operating Ambient Temperature: 0°C ~ +40°C
• Compliance: UL, CE, RoHS compliant

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