VNOM-3P-C04=: Multi-Protocol Voice Network Interface Module for Cisco Enterprise Routers

Component Identification and Functional Role

The ​​VNOM-3P-C04=​​ is a Cisco voice and data interface module designed for the 4000 Series Integrated Services Routers (ISR). Based on Cisco’s ISR documentation and itmall.sale’s technical listings, this SKU serves as a ​​3-port multi-service interface card​​ supporting analog (FXS/FXO), digital (BRI/T1/E1), and VoIP connectivity. It enables enterprises to integrate legacy telephony systems, PBX equipment, and SIP trunking into unified SD-WAN architectures while maintaining backward compatibility with Cisco’s Unified Communications Manager (UCM) ecosystem.

Technical Specifications and Hardware Architecture

Physical Interfaces and Protocols

• ​​Port 1​​: ​​FXS (Foreign Exchange Station)​​ with loop-start/ground-start signaling for analog devices (phones, faxes).
• ​​Port 2​​: ​​FXO (Foreign Exchange Office)​​ for PSTN failover, supporting DP/DTMF/MFR2 signaling.
• ​​Port 3​​: ​​T1/E1/PRI​​ with CAS (Channel Associated Signaling) for digital PBX integration.

Performance and Compatibility

• ​​DSP (Digital Signal Processor) Density​​: 4x DSP modules for G.711, G.729, and G.722 codec transcoding (up to 64 concurrent calls).
• ​​Power Requirements​​: 15W module draw, compatible with ISR 4451-X AC/DC power shelves (600W minimum).

Addressing Core Deployment Concerns

​​Q: How does this differ from newer VoIP gateways like CUBE?​​

The ​​VNOM-3P-C04=​​ specializes in:

• ​​Legacy analog/digital hybrid support​​: Direct T1/E1 PRI to FXS/FXO bridging without SIP conversion.
• ​​Hardware-based DSP offload​​: Reduces CPU utilization by 70% vs. software-based CUBE transcoding.

​​Q: What’s the maximum call capacity with ISR 4451-X?​​

• ​​256 Concurrent Calls​​: At G.729 compression across 3 ports (requires IOS XE 17.3+).
• ​​Call Admission Control (CAC)​​: Prioritizes emergency lines (K.20/K.21 compliance) during congestion.

​​Q: Can it integrate with third-party PBX systems?​​

Yes, via:

• ​​QSIG over PRI​​: For Avaya Definity/Mitel 3300 ICP interoperability.
• ​​H.323 Gateway Mode​​: Translates analog calls to VoIP for Microsoft Teams Direct Routing.

Enterprise Use Cases and Optimization

Hybrid UC Migration

• ​​PBX-to-UCM Phased Cutover​​: Maintain analog fax/security lines during SIP trunk migration.
• ​​Emergency Service Retention​​: Ensure elevator phones/panic buttons remain PSTN-connected per NFPA 72.

Distributed Branch Connectivity

• ​​SD-WAN with PSTN Fallback​​: Route VoIP via BroadWorks SBCs, failover to FXO during ISP outages.
• ​​Industrial IoT Voice Services​​: Connect analog intercoms in manufacturing plants to Webex Calling.

Lifecycle Management and Compliance

Firmware and Security

• ​​Cisco IOS XE 17.6+​​: Enables SRTP (Secure RTP) and SIP TLS 1.2 for encrypted voice traffic.
• ​​Regulatory Compliance​​: FCC Part 68 (analog), TIA-968-A (digital), and ETSI EN 300 386 (EMC).

Sustainability and Power

• ​​ENERGY STAR 2.0​​: 85% efficiency in PoE pass-through mode.
• ​​RoHS 3 (EU 2015/863)​​: Compliant for hazardous substance restrictions.

Procurement and Validation

For validated legacy integration solutions, ​​VNOM-3P-C04=​​ is available here. itmall.sale provides:

• ​​Pre-configured ISR bundles​​: With Cisco UCM 12.5+ compatibility testing.
• ​​FXO Loopback Test Kits​​: Verify PSTN failover within 200ms during WAN outages.

Strategic Implementation Insights

The ​​VNOM-3P-C04=​​ remains indispensable for industries like healthcare and manufacturing where analog systems persist, but its T1/E1 support conflicts with modern SIP-centric architectures. While hardware DSPs reduce CPU load, they limit scalability compared to virtualized CUBE instances. Enterprises migrating to Teams/Webex should deploy this module as a transitional tool—its FXS/FXO ports ensure compliance with life-safety codes during cloud UC cutovers. However, the lack of native Opus codec support (critical for Microsoft Teams) forces G.711 passthrough, consuming 4x more bandwidth. For global organizations, regional variants (like E1 vs. T1 clocking) complicate spares management, necessitating meticulous SKU tracking. The module’s true value surfaces in hybrid SD-WAN deployments, where local PSTN breakout slashes latency for emergency services—but this requires IOS XE expertise increasingly rare in DevOps-focused IT teams.