default routes

When you want to connect a not-Internet-connected router via ethernet to your Ubuntu laptop, but still prefer your laptop’s Wi-Fi connection for Internet routes, you can delete the default route for the ethernet connection:

$ /sbin/ip route | awk '/default/ { print $3 }'
$ sudo route del default gw

^^ where the 192 address is the gw for the ethernet connection

There may be better ways to do this, such as using ifmetric, but the above works for me.