What's going on

When the WAN or Internet LED on your Synology router goes dark or amber, the router cannot establish a physical link or IP lease with your ISP modem. Synology Router Manager (SRM) requires a clean layer-2 hand-off from your modem to route internet traffic. If the physical connection drops or the ISP's DHCP server fails to respond, your Wi-Fi will remain broadcast locally, but no web traffic can pass through.

Symptoms people notice

• Front panel WAN LED is completely off or stuck on amber.
• Devices connect to Wi-Fi normally, but web browsers report "DNS server not found" or "No Internet Connection".
• SRM status dashboard displays "Disconnected" under Network Center.
• Connection breaks entirely following a power outage or modem restart.
• Secondary Synology mesh nodes show signal loss or fail to receive internet pass-through.

Likely causes

• DHCP Handshake Lock: The modem's upstream gateway holds an old ARP/IP lease and refuses to communicate with the Synology router.
• Cabling Quirks: Synology gigabit and 2.5G ports are sensitive to poor pin contact or interference on cheap, damaged Cat5e cabling.
• MAC Address Binding: Cable and fiber providers often lock internet access to the first MAC address detected when the modem boots.
• SRM Smart WAN Mismatch: Dual-WAN settings in SRM might be trying to route primary traffic to an unassigned port.
• Physical Port Surge: Electrical surges passing through coax or Ethernet lines can burn out the WAN port transformer or network chip.

Quick checks first

First, perform a timed power-cycle. Disconnect power from both the modem and your router. Wait two full minutes. Plug the modem back in and let it establish a full connection with your ISP (this takes a few minutes). Once the modem's online light is steady, power on your Synology router.

Next, physically check the WAN port on the back of the device. Swap out the current Ethernet patch cord with a known-good Cat6 cable. Ensure the cable clicks firmly into place on both ends. If the WAN light stays off, try plugging the modem cable directly into a laptop to confirm whether the modem itself is providing an active signal.

When it's a real hardware fault

If the WAN LED stays completely dark regardless of the cable or modem used, the issue may be hardware damage. Lightning storms and grid power surges frequently travel through internet lines, frying the WAN port transceiver chip or micro-transformers on the circuit board.

Inspect the RJ45 socket on the back of the router with a flashlight. Look for bent or misaligned copper pins inside the port. If physical pins are damaged or burnt, the physical layer handshake will fail permanently on that specific port.

Soft resets vs board/panel work

Before assuming the entire router is dead, try a soft reset. Insert a paperclip into the rear RESET button for 4 seconds until you hear a beep; this resets administrator credentials and network settings without erasing your storage data. If SRM was misconfigured, this often restores WAN auto-detection.

If the physical WAN port chip is fried, board-level micro-soldering is rarely practical for consumer routers. However, you can use SRM's built-in flexibility to your advantage. Models like the RT2600ac, WRX560, or RT6600ax allow you to reassign a working LAN port (like LAN 1 or the secondary 2.5G port) as your primary WAN port under Network Center > Internet > Smart WAN, bypassing the damaged port completely.

Next steps

If you need help resolving broader connectivity issues across other networking gear, check out our router problems guide. For hardware comparisons and performance evaluations, visit our main reviews hub or learn more about specific models on our Synology hub.