How do I specify which connected network Mac uses for internet access?

[Riku7]

I had to switch internet service providers, which required me to get a new router as it uses different technology.

If I have my old non-internet router connected to my Mac via ethernet
and my new internet-providing router connected to my Mac via WiFi,
how can I tell my Mac that when I want to access the internet,
it should use the WiFi connection and ignore the ethernet connection?

I'm successfully connected to both but it ignores the functioning WiFi connection if ethernet is connected, and won't load pages.

The reason why I want to keep the old router is that it has been set up with a smart lighting hub and I don't want to risk abruptly losing tons of very intricate setups by moving it to the new router. ISP provider change was rather unplanned, so I want to look into the hub migration sometime later with no stress, now's not a good time.

 

[mfram]

There's a setting in the Network control panel to control "service order" for different interfaces. I would try making the Wifi connection to be the top priority and see if that does what you want. I hope the different routers are providing your interfaces IP addresses in different subnets. If both routers are giving the corresponding interfaces the same subnet (192.168.0.0/24 would be common) then you will have routing problems no matter what. It'll matter of the timing or how the interfaces activate. And that will leave you frustrated.

 

[arw]

If the order/priority setting already solves the issue for you, great.

For me it almost never works reliably so this is what does - independently of the interface order:
As @mfram already mentioned, I also assume ethernet and WiFi are on different subnets.
Then simply enter the DNS server of your WiFi connection into the properties of your ethernet connection.
See attached screenshot: Although ethernet is manually moved to the top, it now uses the WiFi connection for internet connectivity. May require a reboot.

I'm no expert so I don't know how dirty this workaround is...