Yes, exactly; I'm glad the same conclusion was reached.

It should already be permanent, per the configuration files, but it seems
the networking configuration or stack is a bit off. I have seen routes
NOT-add properly when the required NIC was not yet fully up, but I presume
you are using static IP addresses, so that should be unlikely. I've also
seen odd things happen when there was a duplicate IP on the network
somewhere, as the system may try to avoid conflicts for you since those
are generally bad; any chance of that situation happening lately?

Do you see anything useful when trying to get the status of the network
service?

Code:
sudo systemctl status network
For fun, while on the box physically-ish, could you restart your
networking to see if it comes up properly now that the rest of the system
is already working/booted?

Code:
sudo systemctl restart network
As a note, while it is probably generally fine to do, I've seldom worked
with the files under /etc/sysconfig/network/ directly, and would generally
recommend using Yast to configure things when doing so manually. Yast is
pretty robust, particularly around networking, and uses those files
itself; since I have had great luck using Yast, and seldom any problems
like this, it makes me wonder if some of the magical bits may be unhappy
with your changes for some pesky reason. To be fair, you already know I
am not a Z-series expert, so maybe issues there happen more-often in these
cases and all of my experience is for naught.

The route command basically shows the same thing as the 'ip' command, so
that's good, and adding a route manually via ip (or route) does what the
system should be doing behind the scenes. Hopefully we can find something
in the logs (above) that will help us figure things out.

--
Good luck.

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