Yes, your router must be connected to the modem to create a wireless network
The modem is the device that receives the internet signal from your service provider and converts it into data your devices can use. The router takes that data from the modem and broadcasts it as a wireless signal (Wi-Fi) throughout your home. Without the modem connection, the router has no internet to share—it becomes just a box that does nothing useful.
Think of it this way: the modem is your front door to the internet. The router is what lets everyone inside your house use that door at the same time. You need both, and they need to be connected to each other with an ethernet cable.
Key Takeaways
- The modem and router must be connected by an ethernet cable for your Wi-Fi to work.
- The cable plugs into the ethernet port on the back of the modem and the WAN or Internet port on the back of the router.
- If the cable is loose or damaged, you will lose internet on all wireless devices even though the modem itself is working.
- Some internet providers offer a combined modem-router unit, which has both functions built into one device and requires no separate cable.
How the modem and router connect
The connection between modem and router is straightforward: one ethernet cable runs from the modem to the router. On the modem, this cable plugs into the port labeled Ethernet or sometimes LAN (Local Area Network). On the router, it plugs into the port labeled WAN (Wide Area Network), Internet, or Uplink—the label depends on the router brand.
The cable itself is a standard ethernet cable, the same type used to connect computers directly to a modem or router. It has a plastic connector on each end that clicks into place. If the cable comes loose on either end, your wireless network stops working even though the modem is still receiving signal from your service provider.
Check this connection first if your Wi-Fi suddenly stops working but your modem lights are still on. Push the cable firmly into both ports until you hear or feel it click. A loose connection is one of the most common reasons people think their modem is broken when it is actually just unplugged.
What happens if the modem and router are not connected
If the ethernet cable is missing, unplugged, or damaged, the router cannot receive any internet data to broadcast. Your Wi-Fi network will either not appear at all or will appear but have no internet connection—your devices will connect to the network name but show "no internet" or a yellow warning triangle.
The modem itself will continue to work normally. Its lights will show that it is receiving signal and online. But none of that internet reaches your wireless devices because the router has nothing to relay. This is why it is important to check the physical cable before calling your service provider to report an outage.
Combined modem-router units
Some internet providers issue a single device that combines the modem and router into one unit. Common examples include the Xfinity xFi Gateway, the Spectrum Modem Router, and similar all-in-one devices from other providers. These devices have both functions built in, so there is no separate ethernet cable to connect.
If you have a combined unit, you still have a modem and router—they are just in the same physical box. The internal connection between them is already made at the factory. You do not need to do anything to connect them. However, if your provider gave you a separate modem and router, you must connect them with an ethernet cable.
Checking your cable and ports
If your internet is not working, inspect the ethernet cable running between your modem and router. Look for visible damage—kinks, cuts, or crushed sections. Ethernet cables are durable but can be damaged by being pinched under furniture, chewed by pets, or bent too sharply.
Next, make sure the cable is fully inserted into both ports. Push it in firmly until the small clip on the connector clicks into place. Then check that you plugged it into the correct ports: the modem's Ethernet port and the router's WAN or Internet port. If you accidentally plugged the cable into a regular LAN port on the router instead of the WAN port, the router will not receive internet even though the cable is connected.
If the cable looks fine and is in the right ports, try unplugging both devices for 30 seconds, then plugging them back in. This power cycle can reset the connection and clear temporary errors. Wait about two minutes for both devices to fully restart before testing your Wi-Fi.
When to replace the cable
Ethernet cables are inexpensive and straightforward to replace. If you suspect the cable is damaged, you can buy a new one at any electronics store or online for a few dollars. Make sure you get a standard ethernet cable (also called Cat5e, Cat6, or Cat6a—any of these work fine for a modem-to-router connection).
When you install the new cable, plug it into the modem's Ethernet port first, then into the router's WAN or Internet port. The order does not matter for function, but doing it this way makes it easier to see which end goes where. Wait for the router to restart and show a stable internet light before testing your Wi-Fi.
Frequently Asked Questions
Can I use Wi-Fi from the modem instead of the router?
Some modems have built-in Wi-Fi, but it is usually weaker and slower than a dedicated router. If your modem broadcasts Wi-Fi, you can use it, but you will get better coverage and speed by using the router instead. If you want to use only the modem's Wi-Fi, you do not need the router connected—but you will lose the benefits of having a separate router.
What if my router does not have a WAN port?
All routers have a port for the modem connection, but the label varies. Check the back of your router for ports labeled WAN, Internet, Uplink, or sometimes just a different color from the other ports. The manual or the manufacturer's website will show you which port to use. If you cannot find it, contact the router manufacturer's support.
Can I connect the modem and router wirelessly?
No. The modem and router must be connected by an ethernet cable. There is no wireless option for this connection. However, once the router is connected to the modem, you can connect your devices to the router wirelessly.
Does the cable length matter?
Ethernet cables work reliably up to 100 meters (about 330 feet), so length is not a practical concern in a home. A 50-foot cable works just as well as a 6-foot cable. If you need to run the cable a long distance, buy a longer cable rather than trying to extend a short one with adapters.
What if the modem and router are in different rooms?
You will need a longer ethernet cable to run between them. Run the cable along baseboards or through walls if needed. Make sure the cable is not pinched, kinked, or damaged along its length. If running a cable is not practical, some people use powerline adapters or mesh Wi-Fi systems to extend coverage, but the modem and router themselves must still be connected by ethernet.