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The fix depends on whether you want one shared network or two separate ones. For a single shared home or office network, the usual arrangement is one router handling routing and DHCP, with the second router set to Access Point (AP) or bridge mode if its model supports it. If both routers are routing, they may create separate networks and double NAT. Check the intended layout, router settings, and model-specific port instructions before changing cables.
First decide whether you want one network or two
If devices connected through either router should find one another and share local services, aim for one LAN: one device should act as the gateway, and the second router should extend the network in AP or bridge mode. Devices on separate networks may not communicate as expected, as Google Nest’s network guidance explains.
If you deliberately want isolated networks, the second router may remain in Router mode. That choice can be appropriate for separation, but it changes how devices communicate and may introduce double NAT. The correct choice is a topology decision, not a switch setting.
Trace the cables and identify each device
- Write down the path from the internet connection: modem or ISP gateway, primary router, switch, and secondary router. Note which exact ports are connected at each end.
- Check that each device has power and, where available, that Ethernet link lights are on at both ends of each cable.
- Mark which devices connect to the switch and which connect to each router. A switch can sit in different places in a network; the headline alone does not establish the correct wiring for your setup.
If a link light is absent, check that cable and its port before changing network settings. If the links are present but devices cannot reach one another, focus next on router mode, DHCP, and addressing.
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Check whether both routers are routing
Two routers both performing Network Address Translation (NAT) can create separate private networks. This is called double NAT; it can interfere with communication between devices and may cause connectivity or performance problems. It is a possible cause, not a diagnosis based only on having two routers and a switch. Google describes the issue and its effects in its double-NAT guidance.
For one shared LAN, the typical remedy is to configure the secondary router in AP or bridge mode, leaving the main gateway to route traffic and provide DHCP. ASUS documents supported router operating modes, and TP-Link explains AP-mode setup. Follow the instructions for your exact model and firmware; available features can change in AP mode.
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Set DHCP and LAN addressing according to the model
In a shared-network setup, avoid having the secondary device issue conflicting addresses. AP mode often handles the necessary behavior, but its implementation varies. TP-Link’s guidance for certain setups describes disabling DHCP and assigning the secondary device a LAN address in the main router’s subnet. Do not apply those steps blindly: use the relevant manufacturer instructions for both devices, and ensure the chosen address does not conflict with the main router or another device. See TP-Link’s router-to-access-point configuration guidance.
Do these 3 things before closing this tab:
1Clear out junk files and repair common Windows errors2Fix the driver behind crashes, sound loss and screen glitches3Repair Windows errors before they cause bigger problemsAfter changing settings, reconnect a device and check the IP address and default gateway it receives. For a single LAN, the device should receive its network configuration from the intended main gateway. If it receives an unexpected address or gateway, recheck DHCP and the cabling rather than assuming the switch is faulty.
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Use the port layout specified for your router
There is no universal rule that the secondary router’s WAN port must—or must not—be used. Some documented AP configurations connect through LAN-side ports and leave the WAN port unused; another model or operating mode may specify a different arrangement. Check the manual or support instructions for the exact model before moving the cable. ASUS and TP-Link publish mode-specific setup guidance in their ASUS operating-mode instructions and TP-Link AP-mode instructions.
Know what the switch can and cannot fix
An unmanaged Ethernet switch expands the number of wired Ethernet ports. NETGEAR Support says, “An unmanaged Ethernet switch is appropriate” when more ports are needed. It does not turn a router into an access point, stop that router from providing DHCP, or correct double NAT. If the network configuration is wrong, adding a switch will not resolve it; see NETGEAR’s explanation of unmanaged switches.
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Gather these details if the problem remains
- Model numbers for both routers, the switch, and the ISP gateway or modem.
- A cable diagram showing the connected ports at both ends.
- The intended result: one shared LAN or intentionally separate networks.
- The IP address and default gateway shown by a device connected to the network.
- The exact symptom, such as no internet, no link light, or devices unable to discover one another.
Those details determine the right model-specific instructions. Without them, there is no reliable basis to name one universal port arrangement or single root cause.
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