What's going on

When a Ubiquiti gateway (such as a UniFi Dream Machine, USG, or EdgeRouter) shows no WAN link light, the layer-1 physical Ethernet connection or layer-2 DHCP handshake between your router and the upstream ISP modem/ONT has failed. Ubiquiti hardware requires strict signal integrity and link negotiation. If the physical LED is completely dark, the router is not detecting an electrical carrier signal from the upstream modem.

Symptoms people notice

• WAN port link LED on the Ubiquiti gateway is completely unlit
• UniFi Controller reports 'Primary WAN Disconnected' or 'No Internet'
• Modem or ONT link light remains unlit on the connected port
• Internet drops completely while local LAN traffic continues to work
• WAN IP address is displayed as 0.0.0.0 or self-assigned in UniFi or EdgeOS
• WAN light stays off or flashes erratically after a power outage

Likely causes

• ISP ARP/MAC lock: Upstream ISP equipment still holds a lease bound to a previous router MAC address.
• Physical cable degradation: A marginal patch cord fails to maintain continuous contact on all eight copper pins.
• Speed negotiation mismatch: Auto-negotiation fails between high-speed fiber ONTs and Ubiquiti auto-sensing ports.
• VLAN tagging requirements: Fiber service providers require specific VLAN IDs on the WAN interface to acknowledge traffic.
• Ethernet PHY chip failure: A power surge over the incoming line damaged the physical interface transceiver.

Quick checks first

Start by executing a clean reboot sequence. Turn off both the ISP modem/ONT and your Ubiquiti gateway, leaving them unpowered for 5 minutes. This delay forces the provider's node to release old ARP bindings. Power up the modem first, wait until its WAN/Internet lights freeze solid, and then turn on your router.

Next, check the Ethernet patch cable. Ubiquiti ports are sensitive to pin alignment and cable quality; even minor wire degradation can prevent line detection. Swap in a fresh Cat6 cable. If you are using an SFP+ to RJ45 adapter module on a Dream Machine, verify that the module supports the specific link speed of your ONT. For additional routing context, explore our router troubleshooting hub.

When it's a real hardware fault

If power cycling and cable swaps do not restore the port link light, test the WAN port directly by plugging a laptop Ethernet cable into it. If the LED remains dark when connected to a known-working laptop port, the WAN interface PHY chip or magnetics may have been fried by a power surge.

Surge damage across copper coax or Ethernet feeds is common. Fortunately, devices like the UDM-Pro, EdgeRouter 4, or USG-Pro allow you to reassign the WAN WAN1 network to WAN2 or an SFP+ port via software. Remapping lets you run fully on functional secondary ports. To compare hardware features across brands, view our device reviews section.

Soft resets vs board/panel work

Performing soft resets, modifying WAN settings, and updating firmware via recovery mode are straightforward software actions. However, micro-soldering board-level components—like replacing Ethernet transformer magnetics or Ethernet PHY ICs—is not advisable for typical users due to multi-layer board trace fragility.

If all physical ports on your gateway are non-functional, replacing the gateway or placing an intermediate managed switch in front of the WAN port is the safest approach. Read more about hardware setups on our Ubiquiti brand page.

Next steps

If port remapping restores your internet link, continue using the secondary interface and monitor event logs for drops. If the router remains unresponsive across all ports, check our list of supported network devices for compatible hardware options.