Routers & modems

Modem vs router

The modem brings the internet into your home; the router shares it with your devices. Many ISP boxes do both, which is why the terms get mixed up.

Updated By the SpeedTester.pk team

Short answerA modem (or ONT for fibre) connects to your ISP's line and turns its signal into a normal internet connection. A router takes that one connection, shares it with all your devices and creates your Wi-Fi network. A single box that does both is often called a modem-router or gateway.

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Side by side

FeatureModem / ONTRouter
Connects toThe ISP's line (phone line, fibre, cable or mobile network)The modem/ONT, via its WAN port
JobTranslates the line signal to EthernetShares the connection, assigns addresses, firewall, Wi-Fi
Devices it servesOne (the router)All your devices
Who controls itUsually the ISPYou (or the ISP, if it's a combo unit)

The types of modem

  • DSL modem: connects to a telephone socket with a thin RJ11 cable. Speed depends heavily on the length and quality of the copper line (DSL explained).
  • Fibre ONT (optical network terminal): connects to a thin fibre cable, often with a green or blue connector. Has a PON light, and a LOS light that turns red when the fibre signal is lost (fibre explained).
  • Cable modem: connects to a coaxial cable.
  • 4G/5G modem: uses a SIM card and the mobile network; almost always built into a router.

How to tell what you have

Follow the cable from the wall. The first box it reaches is the modem or ONT. If that same box also broadcasts Wi-Fi and has several LAN ports, it's a combo unit, and it may be all you have. If a second box is plugged into it and makes the Wi-Fi, that's your router.

Each box has its own admin page. The router is at your default gateway address (find it); ONTs and cable modems often use 192.168.100.1.

Combo units and bridge mode

ISP-supplied units usually combine modem and router. They're convenient, but their Wi-Fi may be basic, and settings are often locked. You can add your own router behind it, but then two devices are routing (double NAT), which can break port forwarding and gaming NAT types.

The clean fix is bridge mode: the ISP unit only acts as a modem and your router does everything else. Many ISPs enable it on request, since it usually needs their admin access; your router will then need the PPPoE login details (if your connection uses them). Our 192.168.0.1 guide covers the double-NAT symptoms in detail.

Which one is causing my problem?

If the modem/ONT's internet light is red or off, the problem is the line or the ISP, and no router change will help. If the modem is fine but Wi-Fi is slow or drops, the router or its placement is the likely cause. A laptop plugged by cable straight into the modem or combo unit is the quickest way to separate the two.

Our network troubleshooter runs the connection checks for you.

Common questions

What is a modem?

A modem converts the signal on your ISP's line (a phone line for DSL, coaxial cable, or a mobile network) into standard Ethernet data. On fibre connections the equivalent device is called an ONT.

Can I use my own router with an ISP modem?

Usually yes: connect your router's WAN port to the modem or ONT. For the cleanest setup, ask the ISP to put their unit in bridge mode so only your router does routing; otherwise you'll have double NAT.

Is a 4G/5G Wi-Fi device a modem or a router?

Both. Portable and home 4G/5G devices contain a cellular modem and a router in one unit.

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