6

A lot of questions here ask how to be able to do this. My question is different, since at least in Windows 10 connecting WiFi and Ethernet just happens on its own, I just ask what does it actually do.

They even have the same range.

In other words, how does the OS decide which connection to use?

Ethernet and WiFi simultaneously

Improve this question

3 Answers 3

Reset to default
4

Windows sets a metric for interfaces, gateways, and routes to calculate a cost that is associated with using that route. The higher the metric, the higher the cost. This cost will determine the best path to take when sending a packet out on the network.

Considering two or more network interfaces are not disjointed - i.e. they will all get you to the same destinations, then Windows automatically sets a metric based on link speed. And, in Windows 10, connection type.

As an example, if you have both a 1Gbps wired connection and a 802.11AC Wireless connection (connected at a speed of 1.3Gbps) then Windows 10 will choose the following metrics for each interface:

  • Wired - Greater than or equal to 200 Mb and less than 2 Gb = 25
  • Wireless - Greater than or equal to 500 Mb and less than 2 Gb = 30

In this case, Windows will choose the wired connection.

In previous versions of Windows, each of these connections would've received the same metric, and therefore Windows would've chosen the interface based on binding order in your network configuration. Windows 10 removed the binding order feature, and it's unclear how Windows 10 will respond in the case of having two or more interfaces with the same metric.

If you would prefer to have Windows use a different interface than what it automatically decided on, you can manually change the metric of your gateways, routes, and interfaces.

For more information about the automatic metric feature and the metrics assigned to each interface type, as well as how to change it, see here: https://docs.microsoft.com/en-us/troubleshoot/windows-server/networking/automatic-metric-for-ipv4-routes

Improve this answer
2
  • 1
    Does John's Automatic metric fit into this? Also, are you saying it's determined individually for each packet? Let's say if I download something, could each byte theoretically be downloaded by a different interface?
    – LWC
    Commented Oct 1, 2020 at 16:13
  • 2
    @LWC automatic metric is the function in Windows 10 that handles this. Each packet can theoretically go out a different interface if windows thinks they can both deliver the packet to the same destination. But, Windows will choose a interface based on cost. It’s happens per packet.
    – Appleoddity
    Commented Oct 1, 2020 at 17:25
1

Windows will prioritize one of the two connections over the other, and use that connection for all traffic until that connection somehow drops, then switches over to the other until that connection somehow drops.

This effectively means, that if the wifi card is prioritized, and it is slower, your network speeds are reduced until it finally switches over.

Its not possible to see or change which adapter is prioritized. It used to be possible in Windows 7, but that trick no longer works. It is advised to disable wifi if you work on LAN too, to ensure that you get the faster speed, unless you don't need the fast speed.

Improve this answer
4
  • 1
    I was under the impression that the InterfaceIndex returned by Get-NetAdapter determined the order in wich adapters are tried for a connection. The lower the ifIndex, the higher it's priority sort of speak.
    – Lieven Keersmaekers
    Commented Oct 1, 2020 at 11:21
  • 1
    @LievenKeersmaekers That used to work in Windows 7, but haven't seen that working in Windows 10.
    – LPChip
    Commented Oct 1, 2020 at 12:19
  • 1
    That command works in Windows 10 without problems but I assume that's not what you mean. Anyway, a fairly straightforward test (if OP care's) but time consuming would be to monitor network traffic while creating connections and enabling/disabling Wifi/Ethernet card.
    – Lieven Keersmaekers
    Commented Oct 1, 2020 at 13:20
  • 1
    Windows 10 has tightened up on security and controls, and in a machine that has been properly installed and set up, only one connection will be active at one time. Wired if the Metric is ON
    – anon
    Commented Oct 1, 2020 at 13:21
1

If the machine is working properly , Wireless should disconnect when you connect a working Ethernet Connection.

Windows will just use one connection - Wired if available and not both.

It uses the Automatic Metric to do this. See the screen shot below taken from the Network and Sharing Center (Control Panel).

If you think your machine is not working properly, that is, set in the default way, you may wish to run the basic repair steps.

Run DISM / SFC to correct small issues. Also make sure Automatic Metric is enabled.

Open cmd.exe with Run as Administrator.

dism.exe /online /cleanup-image /StartComponentCleanup

dism.exe /online /cleanup-image /restorehealth

SFC /SCANNOW

Restart and test.

enter image description here

Improve this answer
1
  • 1
    My Win10 machine does not disconnect the wireless after the wired connection is plugged in, just as with OP.
    – Bort
    Commented Jul 15, 2021 at 13:12

You must log in to answer this question.

Not the answer you're looking for? Browse other questions tagged .