Take a look at the back of any router or other networking gear, and you’ll see a row of seemingly identical RJ45 ports. However, these ports are not always interchangeable — you’ll typically find one or two ports labelled WAN, while the others may be numbered or marked LAN. Even though they may look the same and even use the same Ethernet cables, these two types of ports serve completely different purposes.

The distinction between WAN and LAN matters the most when you’re setting up a new router or adding new devices to your network. Many devices like TVs, gaming consoles and PCs benefit from a wired link to your network for faster download speeds and connection stability. But if you accidentally plug one of these devices into the wrong port on your router, it may not be able to access the internet.

The WAN port on your networking gear acts as the gateway to the internet, while LAN ports connect devices within your local network and allow them to communicate with each other. Here’s why that distinction matters and what you should keep in mind before plugging an Ethernet cable into either the WAN or LAN ports.

LAN stands for Local Area Network, and refers to the network created entirely within your home or local environment. Devices you connect to your router are automatically added to this network, allowing them to communicate with each other. Features like Apple’s AirPlay, Google Cast and Roku’s screen mirroring rely on this local network connectivity for cross-device communication.

On the other hand, WAN is short for Wide Area Network and serves as the physical link to the outside world, typically the internet. Think of the internet as just another network, but on a global scale. The WAN port is where you plug in the cable originating from your internet service provider. With the right configuration in place, your router will negotiate an internet connection over this port and route traffic from LAN devices through to the internet. The latter is where the term router comes from.

LAN and WAN refer to two different sides of a network connection. Your router assigns each device its own private IP address. At the same time, the router also receives an IP address from the upstream internet service provider’s network. This means the router acts as the bridge between your local network and the wider internet.

Some router brands use different colors to differentiate between WAN and LAN ports, and many routers indicate LAN ports with numbers. The order doesn’t matter in most cases, meaning you could plug a new device into the first or third LAN port. That said, some networking gear may offer a small number of faster LAN ports, so check the manual for exact specifications if you care about maximizing throughput.

Wi-Fi is effectively another way of connecting your devices to your local network, or LAN. But instead of physically plugging in an Ethernet cable, Wi-Fi allows devices to wirelessly communicate with your router.

You may have noticed that phones and other devices remain connected to your Wi-Fi network even in instances when the internet stops working. This happens because Wi-Fi simply provides a wireless link between your local devices, including the router that’s responsible for negotiating internet access over the WAN port. But in the absence of the latter, you’ll still be able to use your Wi-Fi connection to access networked devices like a networked printer or storage server.

That said, many modern routers allow you to create a guest Wi-Fi login that creates a secondary local network or LAN. Devices that connect to a guest network are still allowed to access the internet, but won’t be able to see or communicate with devices on the primary local network. This isolation is a useful security measure since unknown or untrustworthy devices could attempt attacks against vulnerable local devices. Researchers often find vulnerabilities in connected printers and less sophisticated devices.

You can also have multiple Wi-Fi broadcasting stations in a single network. Mesh Wi-Fi systems and access points connect to your primary network either using a cable plugged or even wirelessly. Either way, they extend your LAN beyond the physical port.

So the next time you’re looking to set up a router or connect a new device, remember that WAN and LAN refer to different sides of your network. The WAN port connects to the internet, while LAN refers to the communication channel between local devices. With that in mind, choosing the right port doesn’t feel quite so daunting.