Ttgjyuk

Note: this question has changed while investigating problem to stay up to date.

Note 2: This question is invalid, the described problem is gone. Askubuntu prevents me from deleting it.

Here is my /etc/netplan/01.yaml config on my new 18.04 headless server. The file describes two of my hardware interfaces i may use:

network:
 version: 2
 renderer: networkd
 ethernets:
 enp2s0:
 optional: true
 dhcp4: yes
 wifis:
 wlx0013eff10948:
 access-points:
 "the-network":
 password: "the-password"
 dhcp4: yes

The problem is that Wifi connection sometimes can die. Or there is no connectivity at boot time. The same conditions are for Ethernet interface.

How can i tweak my system to adapt routing table and and etc to these changes? For now, it seems that any hardware change breaks system's "default gateway".

As a result, i can have one or both my interfaces with an assigned IP addresses without working ping in my system. And there is not problem with access point or router behind cable - my setup just cannot survive "changes" and switches..

ifconfig summary

docker0
 (br)

enp2s0 
 (no inet)
lo

tun0

 (openvpn - there is client daemon that needs to be connected to my VPN)

wlx0013eff10948
 (inet 192.168.1.x) = shows as connected, but internet is not working

Less relevant information

wlx0013eff10948 is rtl8192cu USB dongle. I only installed linux-generic-hwe-18.04 for it to appear and work (tested with wicd-curses). As it turns out, there is no problem with WIFI - just the way system handles the lost wifi (or cable) connection.

Sometimes i can see this output appearing in machine's tty:

[ 232.2332] rtlwifi: AP off, try to reconnect now

Exactly at the state when i don't have wifi cable and wifi connection has died, but should be re-established. Which is not happening

How about this version, which will use the preferred network to route packets if it is present? Should this work:

network:
 version: 2
 renderer: networkd
 ethernets:
 enp2s0:
 dhcp4: yes
 optional: true
 dhcp-overrides:
 route-metric: 100
 wifis:
 wlx0013xxx:
 access-points:
 "the-network":
 password: "the-password"
 dhcp4: true
 dhcp4-overrides:
 route-metric: 200 

Try...

An optional device is not required for booting. Normally, networkd will wait some time for device to become configured before proceeding with booting. However, if a device is marked as optional, networkd will not wait for it. This is only supported by networkd, and the default is false.

Source: https://netplan.io/reference

network:
 version: 2
 renderer: networkd
 ethernets:
 enp2s0:
 dhcp4: yes
 dhcp4-overrides: # possibly not functional yet
 route-metric: 100 # possibly not functional yet
 optional: true
 wifis:
 wlx0013xxx:
 access-points:
 "the-network":
 password: "the-password"
 dhcp4: true
 dhcp4-overrides: # possibly not functional yet
 route-metric: 200 # possibly not functional yet