Connecting a Cable Modem to a Router

Connecting a Cable Modem to a Router
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Connecting a cable modem to a router is one of the first tasks when building a home or small business network. Routers used to be large and expensive so we made do without them. With the development of home routers, it makes sense to include one in a network if you can.

They offer many advantages including hardware firewalls, traffic control, internet access control, Quality of Service options for VoiP, it allows the sharing of an internet connection between many computers and can provide wireless network access. The specific features and benefits of a router depend entirely on the model you have, but these are the most common.

Modem to Router

The specific method of connecting the modem will again depend on the type of modem your ISP provides. Some will be USB only, others will be a combination of USB and ethernet. Unfortunately there are no routers with USB input, they are all geared towards network connections. If you have a modem with USB only, you’re going to have to either connect it straight into a PC and use Internet Connection Sharing or get a new, compatible modem with an ethernet connection.

If you have an existing internet connection, your modem should be connected to the wall via a coax or telephone (RJ11) connection. Take a look on the back of the modem to see if you have a USB and/or an ethernet (RJ45) connection.

USB port

Use an Ethernet cable if you have it and connect the modem to the router with it.


The router should have a port labeled something like “Internet”, “WAN” or “Input.” WAN stands for Wide Area Network, which describes the type of network the internet is. Connect the cable from your modem into that port on the router.

Router to Computer

If you previously used the USB connection from the modem to the computer, you are going to have to acquire or use a network port on the PC. Check on the back of it for a port that looks like the RJ45 example in the illustration above. Many newer motherboards have them built-in, but they are available as separate cards if your’s doesn’t have one.

Presuming you have a network port, using the same type of ethernet cable, make another connection between the computer and the router. This time, use Port 1 on the router instead of the input port. You should see a light on both the router and the network port on the computer. That is all there is to physically connecting a cable modem to a router.

So turn on the router, and the PC and give them both time to boot. If all goes well you should have an internet connection immediately. If not, then the router might need some configuration.

My article on basic router configuration is a great place to start if you need to do this.