Modem vs Router: What Is the Difference?
A modem connects you to the internet. A router shares it at home. Here is the difference and when you need both.
A modem connects your home to your internet provider. A router creates your home network and shares that connection with your devices, usually over WiFi.
A modem connects your home to your internet provider. A router creates your home network and shares that connection with your devices, usually over WiFi.
Many providers supply a single box that does both, called a gateway. Here is how they differ and what you actually need.
Modem vs router at a glance
| Modem | Router | |
|---|---|---|
| Job | Talks to your ISP line | Creates the home network |
| Connects to | Cable, DSL, fiber or 5G line | Modem or gateway |
| IP address | Gets your public IP | Gives devices private IPs |
| WiFi | No (unless a gateway) | Yes |
| Typical login | 192.168.100.1 status page | 192.168.1.1 or 192.168.0.1 |
I point people at the WiFi row first, since it is the difference they notice at home.
Do you need both?
- Cable, DSL or fiber: you need a modem or ONT, plus a router. A gateway combines them.
- Gateway from your ISP: you already have both in one box.
- Own router with a gateway: put the gateway in bridge mode to avoid double NAT.
- 5G home internet: the gateway is the modem and router.
I check what box is already there before I suggest buying anything.
How to connect a modem and router
- Turn off the modem and router.
- Connect an Ethernet cable from the modem to the router WAN or Internet port.
- Power on the modem, wait for it to connect, then power on the router.
- Log in to the router and run its setup wizard.
I power the modem first and wait, since the router cannot set up before the line is live.
Should you buy your own?
Buying your own router often gives better WiFi, faster updates and more features than an ISP unit. Buying your own modem can save rental fees on cable plans, but it must be on your ISP approved list.
See how to choose a WiFi router.
I buy my own router first, since it is the box that shapes the WiFi I actually use.
Gateways: modem and router in one box
Many ISPs supply a single box that does both jobs, often called a gateway or hub. It’s convenient: one box, one power socket. But if the WiFi is weak, you can’t upgrade just the router part without either adding another router or switching the gateway to bridge mode.
If your box has a coax, phone line or fibre cable going in and WiFi coming out, it’s a gateway. I spot a gateway by the cable going in and the WiFi coming out.
What about the ONT on fibre?
On fibre connections, a small box called an ONT (Optical Network Terminal) often sits where the fibre enters your home. It does the modem’s job for fibre. Your router plugs into it with an Ethernet cable. Some ISP routers have the ONT built in.
I leave the ONT alone and restart the router first, since the ONT rarely needs touching.
Signs your problem is the modem, not the router
- The modem’s online, DSL or internet light is blinking or off.
- No device can get online, even with a cable plugged straight into the modem.
- Your ISP’s app shows the connection as down.
- Speeds are low even on a wired connection.
If the modem is fine but WiFi is weak or drops, the router is the part to upgrade. If the modem keeps losing its connection, call your provider before buying anything. I trust the lights first, since they tell me which box has actually failed.
Mesh systems and where they fit
A mesh system replaces the router part, not the modem. The main mesh unit plugs into your modem (or the ISP gateway in bridge mode), and the other units spread WiFi around the home.
If your ISP box is a gateway, either switch it to bridge mode or put the mesh in access point mode so only one device is routing. I put the mesh in access point mode when the ISP box is already routing.
Restart a modem and router the right way
- Unplug the router, then the modem (or ONT).
- Wait 30 seconds.
- Plug the modem back in and wait until its online light is steady, usually 1 to 2 minutes.
- Plug the router back in and wait for its internet light.
- Test a website.
Restarting in this order lets the modem connect to your ISP first, so the router gets a proper address when it starts. I wait for the modem light to go steady before I touch the router.
