Cisco NIM-2FXS/4FXOP=

Overview

The Cisco NIM-2FXS/4FXOP= is a voice network interface module designed for ISR 4000 series routers, enabling seamless integration of analog devices and external phone lines without additional hardware. It features two FXS/DID ports for connecting analog phones, fax machines, or paging amplifiers, alongside four FXO ports that link directly to the public switched telephone network. This module simplifies voice infrastructure by consolidating connections within the router, reducing cabling complexity and points of failure while supporting a gradual transition to IP telephony.

Ideal for branch offices and midsize sites that operate a mix of VoIP and legacy analog services, it allows continued use of existing analog endpoints while centralizing call processing on the router. The FXO ports also provide a reliable failover option if SIP trunks experience downtime, ensuring voice traffic remains within a secure and policy-controlled network environment.

Key features

• Two FXS/DID ports support analog devices such as desk phones, fax machines, and paging systems, maintaining compatibility with legacy equipment.
• Four FXO ports enable direct connection to the public switched telephone network, facilitating external voice line integration.
• Online insertion and removal capability allows the module to be added or replaced without shutting down the router, minimizing downtime in critical environments.
• Designed specifically for Cisco ISR 4221, 4321, 4331, 4351, and 4431 routers, ensuring smooth integration with existing chassis and power configurations.
• Centralizes voice and data management through the familiar IOS XE interface, streamlining configuration and monitoring tasks.
• Supports a hybrid voice environment, allowing businesses to preserve investments in analog equipment while moving toward IP telephony at their own pace.

Key specs

• Ports: 2 FXS/DID ports for analog devices
• Ports: 4 FXO ports for PSTN connectivity
• Compatibility: Cisco ISR 4221, 4321, 4331, 4351, and 4431 routers
• Installation: Online insertion and removal supported
• Management: Configured and monitored via Cisco IOS XE

Connectivity and compatibility

This module integrates directly into the ISR 4000 series router chassis, leveraging existing slots and power budgets without requiring additional hardware. The FXS/DID ports connect to internal analog endpoints such as phones and fax machines, while the FXO ports link to external telephone lines from the public switched telephone network. This setup allows voice traffic to flow through the router’s secure network environment, simplifying management and enhancing reliability.

Compatibility with multiple ISR 4000 models ensures that organizations can deploy this module in a variety of branch or midsize office scenarios, maintaining consistent voice service alongside data networking.

Installation and setup

Installing the Cisco NIM-2FXS/4FXOP= is straightforward and designed to minimize disruption. The online insertion and removal feature means the module can be added or replaced without powering down the router, which is crucial for environments where uptime is essential. Configuration and monitoring are handled through the existing IOS XE interface, allowing IT staff to manage the module using familiar tools and workflows.

This ease of installation and management makes it a practical choice for locations with limited on-site IT support, such as retail stores, healthcare clinics, or remote offices.

Ideal uses and environments

The module is well suited to organizations that operate a hybrid voice environment, combining legacy analog devices with modern IP telephony. It fits well in branch offices and midsize sites that require reliable voice connectivity without overhauling existing infrastructure. Retail locations, healthcare facilities, and remote offices benefit from its ability to maintain analog services while integrating voice traffic into a secure, centralized network.

Its failover capability via FXO ports also makes it a strong choice for businesses that need uninterrupted voice service, providing a backup path when SIP trunks are unavailable.

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