How to ensure internet traffic will only go through a wired network connection on a Windows 10 that has multiple network interface?

Question

I used two piece of hardware to construct my home network:

1. A ADSL modem to connect to the ISP for internet connection
2. A google wifi which connects to the ADSL modem and acts a access point.

I have a desktop PC (Windows 10 Pro). Because the said modem has 4 local network port and the desktop PC is physically adjacent to the modem so I connect it to the modem directly. The network speed is faster and the connectivity is more stable this way (Google wifi needs to be restarted form time to time)

However I also want to share a laser printer via the Windows 10 to the rest of the wifi network.

I reckon I can do it by also connect the Desktop PC to the wifi network.

My question:

How can I ensure the internet traffic of the Desktop PC will only go through the wired network while it can share the printer via wifi?

Answer 1

Your problem is that Google WiFi is a router and the ISP's ADSL modem is also a router. This creates a situation of double NAT, where your computer is in the Ethernet segment while the WiFi network is on another, and the two cannot communicate.

If you have no intention of getting more Google WiFi devices in a mesh, meaning that you will only ever have one, you can use the much simpler solution of setting Google WiFi to Bridged Mode, so that it and your modem become one network. You can then share the printer within the local network through Windows. With this method you will lose mesh capability for Google WiFi, which is not required if you only have one.

See Google's article Bridge mode, section "Enable bridge mode on your primary Wifi point", for instructions for setting Google WiFi in Bridged Mode.

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The opposite may also be possible: Putting the modem into bridged mode so it becomes part of the Google WiFi network. This will conserve the mesh function of Google WiFi.

This will require at least turning off the DHCP function on the modem. It might also require allocating the modem and the computer static IP addresses in the segment used by Google WiFi.

For this, you will need to reduce a bit the allocation range of Google WiFi so as to exclude these allocated addresses. The process is described in the Google Set a custom LAN IP:

1. Open the Google Wifi app and tap the tab.
2. Tap Network & General and then Advanced networking and then LAN.
3. In the “Router LAN IP” section, customize your router LAN address and subnet mask.
4. In the “DHCP address pool” section, customize your starting and ending IP addresses.
5. When you’re done, tap Save, then confirm that you want to save these settings.

Once you’ve saved your new LAN settings, your connected devices will briefly disconnect from Wi-Fi. You may need to restart your devices to re-connect them.

Answer 2

I would suggest using port forwarding instead. If you can print to your wireless printer over TCP-IP, then you don’t need to connect your desktop to the wifi at all.

Set your printer up to allow the TCP-IP connection on port 9100 if this setting is not already enabled. Check your printer documentation on how to do this, as it will vary by make and model.

In the Google Wi-Fi configuration, set the printer to have a static DHCP address by doing the following:

• Open the Google Wi-Fi app
• Navigate to the “Advanced Networking” menu
• Select “DHCP IP Reservations”
• In the bottom right, click the plus icon
• Select the device to reserve the address for; Then, enter a static IP address for that device.
• Click “Save”
• Disconnect the device from the Wi-Fi, and reconnect it to ensure it receives the static IP

Next, you will enable port forwarding. Specifically forward port 9100 to the DHCP address you just reserved for the printer.

• Open the Google Wi-Fi app and navigate to the “Advanced Networking” menu
• Select “Port Management” then select “IPv4”
• Select your printer from the list of devices and click “Next”
• Enter the WAN starting port, if required.
• For the Port Range, Enter 9100 - 9100
• Select Type “TCP” and click “Done”

On your computer, you will need to add the printer as a TCP-IP printer. For this you will need to know the public IP address of your Google Wi-Fi mesh. This can be found as the “WAN IP Address” in the Network tab of your Google Wi-Fi app.

• Open Control Panel, and navigate to “Devices and Printers”
• At the top of the window, select “Add a printer”
• Regardless of if the printer appears or not, select “The printer that I want isn’t listed”
• In the window that appears, you will want to choose “Add a printer using a TCP/IP address or hostname” before clicking next
• Change the device type to TCP/IP
• For the Hostname or IP address, enter the public IP of your Google Wi-Fi Mesh
• If you wish to change the alias of the port in case you need to debug it later, put your desired alias in the Port Name field. Otherwise, click next
• The printer should be detected. Name your printer if you would like, then click next
• Follow the rest of the prompts to finish adding your printer

You should now be able to print directly to your wireless printer from anywhere you have internet access. Even if you’re not on the same network as the printer, it should send the print request to the printer. You can now disconnect your computer from your Google Wi-Fi, ensuring all your traffic is going through the wired connection.

Answer 3

Create 2 networks.

As it is, your modem is effectively a gateway (to the internet). Whereas your WiFi is a gateway to the gateway (modem/router). If you create 2 different networks, you will have much greater control over your network(s). Thereby allowing you to choose 1 network as the connection to the Internet, while defining the other as a Local network, that can provide Printer sharing, File sharing, etc...

Then instruct Windows to connect to both of them.

It's as simple as that.

EXAMPLE

NOTE these numbers will not (necessarily) work on your system. As it likely has other numbers assigned.

Imaginary network(s)

Router (gateway to the internet)

Internet side has ip: 4.4.4.10

Router DHCP pool has 254 addresses on the network 192.168.0.1 with a netmask of 255.255.255.0

The Router is a Gateway, and understands how to direct (assigned) IPs from its DHCP pool to the internet IP (4.4.4.10)

Wifi (connected to Router/gateway)

WiFi has the same number of IPs in its DHCP pool on the network 192.168.1.1 with a netmask of 255.255.255.0

You instruct Windows to connect to both networks. Windows will discover automatically which route makes the internet available. But will still recognize that the other network exists, and is available.

Once you've made these connection(s) in Windows "Network Preferences". Windows will remember them, and you can simply Right-click, and Connect, or Disconnect as needed / desired. Which "Forces" the connection to whichever you choose.

If you want to enjoy File sharing, Local Printers, and Multimedia files. Ensure that you connect all of those facilities to your WiFi. Which will then comprise your "Local Network".