I'm not sure my meaning, or maybe tone, came through properly. If you
felt I snapped, as in spoke harshly, please understand that was not my
intention.

Whether or not the 'routes' file syntax or use has changed between SLES 11
and 12, I do not know, as I've never tried modifying it directly, but
instead have always setup routes (rarely, admittedly) via Yast which has
worked well.

Assuming you can modify the system in a way that is persistent across
reboots using Yast, you should be able to determine what the right change
is for adding a given route, whether that's modifying the
/etc/sysconfig/netowrk/routes file itself, or something else. I could
setup another route on a test box and let you know, but my home network is
pretty simple/flat/basic so while I could define them, I would not have a
way to test them to ensure they work despite the configuration changes.
Still, what I would do is use Yast to make the change, and then look at
the snapshot difference automatically captured by Yast and see which files
change, and how. I could then rollback the filesystem to before the
change and try again with the manual (file) changes and see if the changes
still work and are persistent across reboots.

--
Good luck.

If you find this post helpful and are logged into the web interface,
show your appreciation and click on the star below...