Network Connection Priority

[zakko]

Hi there,

my current laptop setting aims to usually connect wired to my network and only if there's no LAN cable connected, WLAN connection should jump in at startup. I automate this by setting the Ethernet priority to 100 and Wireless to 10, always enabled.

Every now and then this priority setting is not taken into account by the system. Unfortunately this is not reproducible. At best it is only a wrongly displayed network icon, but connection speed hints to an unintended WLAN connection. Anyway I wonder if there's an option to fix this by myself or if maybe the Mint devs could take some action to harden the connection priorities? Are there any logs somewhere, to get a clearer picture of what's happening in the error case?



I'm running an up-to-date Mint 20.1. with no (or at least very conservative) system tweaks.

[t42]

... connection speed hints to an unintended WLAN connection.

You need to monitor network interfaces on the system not relying on hints )
Among many tools there is a simple and convenient network load monitor bwm-ng. To install it

Code: Select all

sudo apt-get install bwm-ng

to start

Code: Select all

bwm-ng

pressing t will cycle through output options.

[m00tpoint]

You can also use the "ip route" command to see what's happening. If both interfaces are up, you will see 2 default entries. The one for your eXXXXXX interface should have a lower metric than the wXXXXXX interface. If only one interface is up, you'll only see one default route.

m00tpoint

[zakko]

Now I confused the connections with a bit different setting. I booted Mint up to the login screen without a LAN cable connected, plugged in the LAN cable and logged in. I see the LAN connection icon, but the "Multi-Core System Monitor" applet (https://cinnamon-spices.linuxmint.com/applets/view/79) clearly shows traffic going over the wXXXXXX interface.

So it's not a question of hints anymore and both interfaces are up ("ip route" also showed this).

Regarding the setting/confusion I posted now, I'm not clear of what to expect. When does the connection priority come into play? And at what point is the priority evaluated, especially if a connection via the eXXXXXX interface is established much later in the startup process?

Unfortunately the setting described in my inital post is not reproducible. It just drops by once in a while. So I can't dig any further on that specific case.

Maybe someone knows the things that are supposed to happen during boot and login with changing availability of the two interfaces. Would be cool to get some insights about what to expect.