Debian 12 MESA ethernet with wifi configuration

I’m in the process of configuring new computer to upgrade an existing system. Right now I’m stuck at getting network to work with both, the MESA ethernet and wifi LAN.

I set up the MESA ethernet in /etc/network/interfaces as per the Debian 12 installation document. This part works fine. However, after configuring my wifi internet connection (via the GUI tool in the taskbar), the system appears to use the MESA ethernet as the default route, and the wifi connection quits working. 

If I try to configure MESA ethernet via the GUI tool, the connection appears to work for a few minutes but then disconnects.
I THINK what I want is to specify the MESA  ethernet connection as not providing the default route.


I would also appreciate some clarification as to what the various tools do and if I should be using them. (NetworkManager, networking daemon, etc) I would prefer not having any automatic connections happening on this system.
 

What address are you using for the real time interface?

Its best to use the 10.10.10.x range for the real time interface
as this does not overlap existing NAT ranges.

Please watch my video

Networking fundamentals is discussed about 16 minutes in
You have to understand this to get the two NICs working.
After that it is easy!

So you configure all your network interfaces from the gui. The funny thing is that this is the second time around with this specific computer (I messed up something pretty badly and just started again from scratch) and the first time around it worked perfectly. The only thing I did different this time is I unchecked the gnome gui during installation. (Xfce on both)

Yes, I have the MESA board set to 10.10.10.10 and 10.10.10.11 on the nic.

Turns out it was an issue with my router.

Thanks.

Yes, that's what I did. Sorry if I wasn't clear enough.

Original issue was that I could get both networks up and working:

1. ethernet connection to MESA baord with static IP set to 10.10.10.2
2. wifi connection to LAN

But whenever I tried connecting them concurrently, my connection to LAN no longer worked.
The problem with LAN turned out to be a router configuration issue.

There's still an issue with the GUI NetworkManagemer Applet. When I configure the Ethernet connection with static IP address via the GUI, it connects and then disconnects spuriously.

 When I configure the same connection  via the /etc/network/interfaces file, the connection works without issues. I'm fine with this; I'm just posting here for posterity.

Thanks
 

Make sure you have also set the network connection for your ethernet port to static. Even though I had an IP set in the configs, it was still set for DHCP, which caused a disconnect issue similar to what you described.