UK What a router is
A router is a network device that connects two or more separate networks and decides where each packet of data should go next. It works at Layer 3 of the OSI model, reading the destination IP address on each packet and checking it against a routing table, a list of known networks and the best next hop towards each one.
That is what sets it apart from a switch. A switch moves frames between devices on the same local network using their hardware MAC addresses, while a router moves packets between networks using IP addresses. Our explainer on how an Ethernet switch works covers the Layer 2 side.
On the internet, thousands of routers pass each packet along until it reaches the network it was addressed to. On a site, one router usually sits at the edge, between the local network and the internet provider.
What a router does on a typical network
The box most people call a router does several jobs at once. Routing is only the first of them.
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Routing. Forwards traffic between the local network and the internet, and between internal networks or VLANs where a site has several.
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NAT. Network address translation lets every device on the site share one public IP address, rewriting addresses as traffic passes through.
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DHCP. Hands out local IP addresses, gateway and DNS settings automatically to each device that joins the network.
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Firewall and VPN. Blocks unrequested traffic from outside, and builds encrypted VPN tunnels to other sites or remote users.
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Wi-Fi. A wireless router adds a built-in access point. Larger sites keep the two apart, as our guide to what a wireless access point does explains.
Router vs modem, switch and access point
Home equipment often combines all four in one box, which is why the names get mixed up. On larger and industrial networks they are usually separate devices.
| Device | OSI layer | Connects | Uses | Main job |
|---|---|---|---|---|
| Modem | Layers 1 and 2 | The site to the provider’s line | Line signals | Converts data to and from the line or radio signal |
| Router | Layer 3 | Separate networks | IP addresses | Forwards packets between networks, NAT, firewall |
| Switch | Layer 2 | Devices on one network | MAC addresses | Moves frames between ports |
| Access point | Layer 2 | Wireless devices to the wired network | MAC addresses | Bridges Wi-Fi to Ethernet |
A modem gets a site onto the provider’s network. The router then decides what goes in and out, and the switch and access points connect everything inside.
Industrial and cellular routers
An industrial router does the same work as an office router, built for a cabinet, a vehicle or a remote site. Typical features include DIN-rail mounting, a wide-range DC input, fanless operation over extended temperatures, and serial ports or protocol support for connecting PLCs and meters.
Many remote sites have no wired internet, so industrial routers often connect over 4G LTE or 5G. A cellular router is a router with a built-in cellular modem, and dual-SIM models switch to a second mobile network if the first fails. Where one link is not enough, cellular bonding combines several mobile connections into one faster, more resilient link.
Keeping a router secure
Because the router sits between the site and the outside world, it is the first thing an attacker meets. A few habits matter more than any feature list.
- Change default credentials and turn off remote management on the internet side unless it runs over a VPN.
- Keep the firmware updated. Router firmware contains the routing, firewall and VPN software, and makers patch security flaws in it regularly.
- Open only the ports you need. Port forwarding exposes a device inside the network, so a VPN is usually the safer way to reach machines remotely.
- Separate networks with VLANs. Keep machines, cameras and office devices apart so a problem on one cannot spread to the others.
Industrial sites often follow IEC 62443, the security standard for industrial automation and control systems, which sets out zones, conduits and access rules for exactly this purpose.
When an edge computer does the routing
On a remote asset, a separate router is one more box, power supply and failure point. Many of our industrial IoT gateways take a 4G or 5G module internally and can route traffic, run a firewall and hold a VPN tunnel for the machines behind them, while also collecting and processing their data. Our white paper on integrating 4G, LTE and 5G connectivity covers modules, antennas and carrier choice.
Quick answers on routers
Routers: common questions
Do I need a router if I have a modem?
Usually, yes. A modem connects one device to the provider. A router shares that connection between many devices and protects them with NAT and a firewall. Many provider boxes combine both.
Can a router work without the internet?
Yes. A router still connects the devices on its local network and routes between internal networks. Only internet access needs the provider link.
Can I use a router as a switch?
Partly. The LAN ports on most routers are a small built-in switch, so devices plugged into them can talk to each other. For many ports, add a dedicated switch.
What is a 5G router?
A router with a built-in 5G modem. It connects a site or vehicle to the internet over a 5G mobile network instead of a wired line, usually falling back to 4G where 5G is not available.
What is the difference between a router and an access point?
Networks against wireless clients. A router connects separate networks and controls traffic between them. An access point connects Wi-Fi devices to an existing wired network.
We fit the cellular modules, antennas and network ports each system needs as standard, set up routing, firewall and VPN where the project needs them, and test every connection before the system ships.