NIM-4FXO – 4-Port FXO Voice – Analog NIM – Cisco 4000 ISR

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NIM-4FXO Description

The NIM-4FXO is a Cisco analog voice Network Interface Module for the NIM slots of Cisco 4300 and 4400 Series ISRs that terminate PSTN or PBX lines at a branch voice gateway. The module has four FXO line-side voice ports with ground start and loop start signaling, battery reversal detection and caller ID, plus onboard DSP, straight-through 2-wire cabling and online insertion and removal. Cisco IOS XE 3.13.4 or later and the Unified Communications technology package are required, and the module weighs 0.44 lb (200 g).

Quick Specs

Parameter

Specification

Product ID

NIM-4FXO

Product type

4-port FXO Network Interface Module

Cisco ordering description

4-port Network Interface Module – FXO (Universal)

Total ports

4 FXO voice ports

Analog interface role

Foreign Exchange Office line interface

ISR G2 comparison

VIC2-4FXO

Supported router context

Cisco 4000 Series ISR NIM slots; Cisco 4300 and 4400 Series support context

Cisco IOS XE release for this SKU

XE3.13.4, XE3.14.3, XE3.15.1, XE3.16 and above

Voice package requirement

Minimum Unified Communications technology package for voice applications

DSP design

Onboard DSP on the voice NIM; no dedicated motherboard PVDM required for this voice module family

OIR support

Supported in Cisco 4000 Series ISR NIM slots; managed OIR requires no active calls

Weight

0.44 lb (200 g)

Application Scenarios

PSTN Trunks At A Branch

A branch voice gateway terminates up to four analog PSTN lines from the carrier on the FXO ports, using loop start or ground start signaling.

Line Side Of An Existing PBX

An office that keeps its PBX links four of the PBX’s analog extension ports to the FXO ports, so the router can carry those calls across the IP voice network.

Product Comparison

Parameter

NIM-4FXO

NIM-2FXO

NIM-2FXS/4FXO

Total ports

4 FXO ports

2 FXO ports

2 FXS, FXS-E and DID ports and 4 FXO ports

Product description

4-port NIM, FXO (Universal)

2-port NIM, FXO (Universal)

2-Port FXS/FXS-E/DID and 4-Port FXO Network Interface Module

Cisco IOS XE release

XE3.13.4, XE3.14.3, XE3.15.1, XE3.16 and above

XE3.13.4, XE3.14.3, XE3.15.1, XE3.16 and above

XE3.14.3, XE3.15.1, XE3.16 and above

DSP design

Onboard DSP; no PVDM required

Onboard DSP; no PVDM required

Onboard DSP; no PVDM required

Supported host

Cisco 4300 and 4400 Series ISR NIM slots

Cisco 4300 and 4400 Series ISR NIM slots

Cisco 4300 and 4400 Series ISR NIM slots

Weight

0.44 lb (200 g)

0.42 lb (191 g)

0.52 lb (236 g)

NIM-4FXO provides four FXO ports for PSTN or PBX lines, while NIM-2FXO provides two, so the number of line-side connections to terminate decides between them. A site that also needs station-side FXS, FXS-E or DID ports in the same slot needs NIM-2FXS/4FXO, which keeps four FXO ports and adds two FXS-class ports at 0.52 lb (236 g) against 0.44 lb (200 g). NIM-4FXO supports ground start and loop start, battery reversal detection and caller ID. All three modules include onboard DSP, so none needs a PVDM.

Ordering Checklist

  • Supported hosts: Order for the NIM slots of Cisco 4300 and 4400 Series ISRs; the datasheet does not list Cisco 2900 or 3900 Series, so the module cannot be ordered for those routers.

Specifications

Parameter Specification Parameter Specification
Product ID NIM-4FXO Product type FXO analog voice Network Interface Module
Cisco ordering description 4-port Network Interface Module – FXO (Universal) Total ports 4 FXO voice ports
Analog interface role Foreign Exchange Office line interface ISR G2 comparison VIC2-4FXO
Supported router family Cisco 4000 Series Integrated Services Routers Documented ISR series context Cisco 4300 and 4400 Series ISRs
Unsupported ISR family Not supported with Cisco 2900 and 3900 Series ISRs Cisco IOS XE release for this SKU XE3.13.4, XE3.14.3, XE3.15.1, XE3.16 and above
Voice package requirement Minimum Unified Communications technology package for voice applications DSP design Onboard DSP on the voice NIM family
Motherboard PVDM requirement No dedicated packet voice DSP module required on the router motherboard for this voice NIM family Voice-port configuration form voice-port slot/subunit/subslot
FXO signaling options groundStart or loopStart Dialing method options DTMF, MF, or pulse
Call progress tone setting cptone locale under voice-port configuration Ring detection setting ring number under FXO voice-port configuration
FXO connection role PBX, key system, off-premises PSTN connection, or analog CAMA trunk service FXO feature notes Caller ID, battery reversal detection, cable detection, and overload protection
OIR support FXS, FXO, E/M, and BRI NIMs can be inserted into supported Cisco 4000 Series ISR NIM slots without powering off the router Managed OIR restriction Managed OIR is not supported with active calls
Cabling note Straight-through 2-wire cable for NIM FXO and FXS port connections Network management Remote and local configuration, monitoring, and troubleshooting from Cisco IOS XE Software CLI
Analog NIM jumper note No jumpers to set on NIM analog modules Weight 0.44 lb (200 g)

Quality Certifications

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    Sharon Bell
    Posted on 30/03/2026
    Verified Buyer
    4.0

    My concerns about authenticity were completely unfounded. Real product, real value. Invoice formatting was a bit different from what our AP system expects, but workable.

    Hiroshi Johansson
    Posted on 09/03/2026
    Verified Buyer
    4.0

    Pleased with the experience. Will be back. Shipping took a couple extra days, but product itself is perfect.

    Kathleen Lewis
    Posted on 03/02/2026
    Verified Buyer
    4.0

    Reorder process is so smooth we don’t think twice about it anymore. Shipping took a couple extra days, but product itself is perfect.

    Gandalf
    Posted on 22/08/2024
    Verified Buyer
    5.0

    A swift arrival. The package was secure.

    IT Admin
    Posted on 12/04/2024
    Verified Buyer
    5.0

    Authentic Cisco module. Works as expected.

Questions & Answers

  • Which routers can host NIM-4FXO?

    NIM-4FXO fits the NIM slots of Cisco 4300 and 4400 Series ISRs. Cisco 2900 and 3900 Series ISRs do not support the module. The module carries an onboard DSP, so the router needs no PVDM. Managed OIR is not supported with active calls.
  • Which Cisco IOS XE release does NIM-4FXO need?

    NIM-4FXO needs Cisco IOS XE 3.13.4 or later, with documented releases XE3.13.4, XE3.14.3, XE3.15.1 and XE3.16 and above. Voice use also needs at least the Unified Communications technology package, and no PVDM is required on the router motherboard.
  • Which call control protocols does NIM-4FXO support on its FXO ports?

    NIM-4FXO supports Cisco Unified Communications Manager with SCCP, H.323, SIP and MGCP 1.0. The FXO ports also provide CDR data, cable detection and overload protection. Software configures the ports for the telephony standards of any country, so one module can serve branches in different regions.
  • Can NIM-4FXO carry an analog CAMA trunk for E-911?

    Yes, in North America only. An FXO port on NIM-4FXO can connect to an analog CAMA trunk to deliver E-911 calls. Outside North America the CAMA option does not apply, so use the standard ground start or loop start PSTN connection on those ports.
  • Can NIM-4FXO be hot swapped while the Cisco 4000 Series router is running?

    Only as managed online insertion and removal. Surprise OIR is not supported on NIM-4FXO, and managed OIR is not supported while calls are active. Run show voice call summary first and confirm every port shows ONHOOK before you remove the module.
  • Does NIM-4FXO support the clock-participate command?

    No. The Cisco voice NIM data sheet states that FXO and FXS NIMs, including NIM-4FXO, do not support the clock-participate command. Do not plan clock synchronization of the analog ports through that command, and take timing for the router from its WAN or digital interfaces.
  • Which signaling and dialing defaults apply on a NIM-4FXO voice port?

    Per the Cisco voice and fax NIM configuration guide, a voice port on NIM-4FXO defaults to loopStart signaling, DTMF dialing, the us call progress tone and a ring number of 1. Use the signal command to switch to groundStart when the PBX or carrier line requires it.

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DataSheet Downloads

  • NIM-4FXO Datasheet