In enterprise networking, reliability and adaptability are everything. One feature that helps companies extend the reach of 5G and improve performance—especially in fixed sites and buildings with poor signal or vehicles on the move—is captive modem functionality. It bridges the gap between where your router needs to be and where your 5G signal is strongest, providing better coverage without added complexity.
It’s not a standalone device, but a smart mode of operation that enables seamless pairing of Ericsson Cradlepoint 5G routers and 5G adapters, providing overall better performance. Hence, they act like a single powerful device, even if they are in different locations. For businesses navigating 5G, poor indoor signal, or vehicle-based connectivity, captive modem functionality makes a difference.
What is captive modem?
Captive modem functionality is enabled through Ericsson Cradlepoint’s NetCloud management, which allows a router to function as if a remote cellular adapter’s modem were part of the same device, improving 5G performance. Even if the router and adapter are in different locations, captive modem links them as a single entity.
Think of it this way: imagine your router is like a stereo system in a room that receives no radio signal. Instead of placing a second antenna inside the stereo (which still won't help), you can place an external antenna by the window and connect it, so your stereo now acts as if the antenna is built in. That’s essentially what captive modem mode does: it makes the router and adapter work together like one device to achieve higher performance.
How it works: captive modem mode extends 5G reach
Usually, routers are installed wherever there’s power, often tucked away in places like wiring closets, basements, or server rooms. However, those locations aren’t always ideal spots for cellular propagation, and cellular coverage is usually weak. Instead of installing a second modem into the router, place a cellular adapter where the signal is strongest and ensure a clear line of sight to the radio tower, ideally near a window or on the roof.
Captive modem mode allows a cellular adapter to function as though its modem is embedded within the router. This provides a strong, high-quality cellular signal and extends 5G reach without the need to physically position the router in that location, which could be too far away from other networking gear. With captive modem mode, Ericsson Cradlepoint’s NetCloud software treats the adapter and router as one logical unit, and the networking equipment can remain hidden from view.
This has multiple benefits:
- The router and adapter share a single NetCloud license
- Network policies and failover settings can be managed centrally
- The setup functions as a unified system, even if physically separate
Why it matters
5G performance is highly dependent on placement and line of sight to the cell tower. Captive modem mode enables the optimization of cellular signals and becomes even more powerful when combined with SD-WAN. With SD-WAN, the network can intelligently monitor and manage traffic across multiple WAN links—including embedded modems, captive modems, and wired connections. This ensures real-time application performance, automatic failover, and traffic optimization. For example, if the signal quality drops on one carrier, SD-WAN can quickly switch to another, helping to avoid service disruptions and improve uptime.
Here are some practical applications of captive modem:
- In-building deployments: Place the adapter where the signal is strongest while keeping the router near users or systems.
- Vehicle use cases: In mobile scenarios, such as police cars, the router may be located in the trunk (resulting in poor coverage), while a router and antenna combo is roof-mounted for optimal 5G signal reception plus a wider Wi-Fi range.
- Failover and dual-SIM: Use the embedded modem and captive modem mode together for dual-modem redundancy or carrier switching for optimal coverage.
Real-world example: captive modem mode in action
UK-based housebuilder Crest Nicholson faced a major challenge when relocating its headquarters: fiber connectivity wasn’t ready in time. To support operations for over 300 employees, they deployed one Ericsson Cradlepoint E3000 router with three rooftop-mounted 5G adapters, each equipped with a different SIM. With captive modem mode activated, the router and adapters were managed as a single device. This setup provided over 1 Gbps connectivity via multiple SIMs, with SD-WAN handling seamless failover. A stable and reliable internet connection was established for the entire office and all users. Once fiber was installed, the setup continued to serve as a high-performance solution, ensuring 100% uptime for mission-critical applications and users.
A designed-in feature
Ericsson Cradlepoint first introduced the captive modem feature in its enterprise series routers and later extended it to mobile solutions. We understood early on that 5G wasn't just about speed—it also presented new challenges, such as signals not penetrating walls or concrete. Captive modem mode was designed with that in mind, allowing you to place the modem where the signal is strongest without complicating things and providing greater flexibility. And if you’re setting up temporary sites or waiting on fiber, this mode provides you with reliable, high-speed internet right out of the box by enhancing coverage in areas with poor signal.
Explore our routers and adapters with captive modem functionality.