Dealing with the situation that some LAN network consisting of multiple connected devices without the access to the Internet needs some work, while simultaneously requiring access the Internet from my laptop over the wireless.
The problem is that NetworkManager prioritizes wired paths for the access
to the Internet over wired networks. The actual path priority can be shown
The output on my machine confirms that the wired connection on the
enp0s31f6 takes precedence:
Kernel IP routing table Destination Gateway Genmask Flags Metric Ref Use Iface 0.0.0.0 192.168.20.1 0.0.0.0 UG 10 0 0 enp0s31f6 0.0.0.0 192.168.2.1 0.0.0.0 UG 3003 0 0 wlp4s0 192.168.2.0 0.0.0.0 255.255.255.0 U 3003 0 0 wlp4s0 192.168.20.0 0.0.0.0 255.255.255.0 U 10 0 0 enp0s31f6 192.168.250.0 0.0.0.0 255.255.255.0 U 425 0 0 anbox0
The entries are sorted by the priority from the most preferred to the
least. The proper solution would be to learn to modify the routes using the
route command we used to print the routes out. In a hurry, I have
resorted to the hacky solution that wraps away the hard parts. Enter
yay -S ifmetric
No the priorities can be changed straight away without the need for understanding anything else:
sudo ifmetric enp0s31f6 10 sudo ifmetric wlp4s0 9
The first line is unnecessary as the 10 is the priority assigned to the wired network automatically, but it is included here for a good measure.
The priority numbers chosen are arbitrary, the only important bit is that
the lower the number, the higher the position in the IP routing table,
meaning the higher the priority to choose which interface is used for the
Internet access. We can confirm now that the wireless interface
has the highest priority, providing Internet access over the wireless
connection while simultaneously permits access to the devices on the
isolated network over LAN:
Destination Gateway Genmask Flags Metric Ref Use Iface 0.0.0.0 192.168.2.1 0.0.0.0 UG 9 0 0 wlp4s0 0.0.0.0 192.168.20.1 0.0.0.0 UG 10 0 0 enp0s31f6 192.168.2.0 0.0.0.0 255.255.255.0 U 9 0 0 wlp4s0 192.168.20.0 0.0.0.0 255.255.255.0 U 10 0 0 enp0s31f6 192.168.250.0 0.0.0.0 255.255.255.0 U 425 0 0 anbox0
This is a 80th post of #100daystooffload.