How to Connect Your Router to a Fiber ONT

Fiber ONT and router roles

A fiber ONT, or optical network terminal, sits at the point where the fiber line enters your home. It converts the provider's optical signal into an Ethernet signal that standard networking equipment can use. The router connects to that Ethernet signal and creates your local network, including Wi-Fi. If you are comparing the boxes at your installation, the ONT does the same job in a fiber connection that a cable modem does for cable internet. See ONT vs Modem.

Some fiber installations bundle an ONT and router in one unit. In that case you may not need a separate router at all. If you have a standalone ONT, keep reading: the connection is one Ethernet cable between the ONT and your router.

Connect the ONT to the router WAN port

On the ONT, look for an Ethernet port. It may be labeled LAN, Ethernet, or Internet. Connect one end of an Ethernet cable there. On the router, find the port labeled WAN or Internet. It is normally separate from the LAN ports and may be a different color. Plug the other end of the cable into the WAN port. For a closer look at router ports, see Router Ports Explained.

Do not plug the ONT into a phone-style jack or into the router's USB port. Fiber service uses an Ethernet handoff on the ONT, and the router expects that handoff on its WAN port. If your router has several LAN ports, leave those for your computers, game consoles, or network switch.

Use the WAN port, not a LAN port

The WAN port is the router's connection to the outside network. The LAN ports connect your devices to the router. If you plug the ONT into a LAN port instead of the WAN port, the router does not know where the internet connection is coming from. The role of each port is described in LAN vs WAN.

If your router has multiple ports that can serve as WAN, choose the one recommended by the router's setup process. On most routers the default WAN port is clearly marked. If you are unsure, check the router's quick-start guide or app. Do not enable bridge mode or access point mode for this main connection unless you are specifically extending another router; those modes are for different layouts. For an explanation, see Router Bridge Mode Explained.

Check status lights and router login

After the cable is connected, power on the ONT first and let it finish starting. Then power on the router. The ONT should show an Ethernet link, and the router should show a WAN connection. If a light does not come on, reseat both ends of the cable and confirm you are using the WAN port. For common connection failures, see How to Troubleshoot a Router With No Internet.

Next, log in to the router admin page. Most routers show a status page that reports whether the WAN port has received an internet address. If the page shows no address, review the WAN connection settings on the router. The general login process is covered in How to Log In to Your Router's Admin Page.

• ONT power light is on.
• ONT Ethernet port shows a link.
• Router WAN light shows a link.
• Router admin page reports Internet connected.

Provider settings: PPPoE, VLAN, DHCP

Most fiber providers hand off internet to the ONT using DHCP. The router automatically requests an address and the connection works as soon as the cable is plugged in. Some providers still use PPPoE with a username and password, and others require a VLAN tag on the WAN connection. If your internet provider gave you those settings, enter them in the router's WAN section. Background on both options is available in PPPoE Explained and VLAN Tagging Explained.

Do not enter PPPoE or VLAN values unless your provider asks for them. Guessing can stop the router from completing the connection. If a computer plugged directly into the ONT already gets an internet address, the router will usually work with DHCP as well.

If the ONT has routing built in

Some fiber providers install a combined ONT and router. If you want to keep that device, you do not need an extra router unless you want more Wi-Fi coverage or features. If you prefer your own router, ask the provider about putting the combined device in bridge mode so that your router can handle the network. That process is described in Router Bridge Mode Explained.

An ONT-only unit, by contrast, does not create Wi-Fi. You need a router between it and your devices. If you are choosing a router for a fiber connection, look for a model with a WAN port that matches your internet speed, a current Wi-Fi generation, and good security features. The buying guides below can help you compare options.

What to pick for your use

Questions

Do I need a fiber ONT and a router?

Yes in most fiber homes. The ONT converts fiber optic light into Ethernet, and the router manages your local network and Wi-Fi. Some providers supply a combined ONT and router; in that case the two are in one box.

Can I connect my router directly to the fiber wall outlet?

Usually no. The router's WAN port expects Ethernet, not an optical fiber signal. The ONT is the device that makes the fiber signal usable by the router.

What Ethernet cable should I use between the ONT and router?

Use a standard Ethernet cable long enough to reach both devices. The exact category depends on your provider's speed, but a modern router with a multi-gig WAN port will need a cable that supports that link speed.

What should I do if the router shows no internet after connecting the ONT?

Check the cable connection, confirm it is in the WAN port, restart the ONT then the router, and review the WAN settings. Your provider may require PPPoE or VLAN settings. Start with the checklist in this article.

Should I change the Wi-Fi password after connecting a new router?

Yes. Choose WPA3 if your router and devices support it. The Wi-Fi Alliance lists WPA3 as the latest security standard and requires it for current certified devices. Change the default admin password as well.

Can my router work if the ONT has Wi-Fi built in?

It can, but you should avoid running two routers at once if it creates double NAT. Put the provider device in bridge mode or access point mode so your router can handle the connection. See Router Bridge Mode Explained.