investigate Hetzner CentOS 8 Gateway issue

[backstreetkiwi]

In #194 a hotfix was provided (and released as Version 1.0.1) to solve a problem with the CentOS8 based clusters on Hetzner/HCloud:

After their first reboot after the update of all software, the protected nodes had a default gateway with the highest priority (=lowest metric) pointing to 10.0.0.1. I guess that it somehow came via DHCP. Unfortunately it prevented internet access from the nodes.

example:

$ ip route
default via 10.0.0.1 dev ens10 proto dhcp metric 100 
default via 172.31.1.1 dev eth0 proto dhcp metric 101 
10.0.0.0/16 via 10.0.0.1 dev ens10 proto dhcp metric 100 
10.0.0.1 dev ens10 proto dhcp scope link metric 100 
172.31.1.1 dev eth0 proto dhcp scope link metric 101

The aforementioned hotfix only erased the first line after each reboot which mitigated the effects but not really solved the problem. With this task, we should further investigate and properly solve the issue.

[backstreetkiwi]

The custom made K3s clusters have not been used in years, so we should drop this issue. @Jimvin

[backstreetkiwi]

T2 is discontinued