If you edit the sysctl.conf, you may or may not know that changes aren’t applied immediately without further action.
You either need to reboot or execute one of the two following commands immediately (to apply without rebooting)
The non-systemd way (typically for 12.2 and earlier)
sysctl -p
The systemd way (12.3 and later although the above should still work indefinitely)
systemctl restart systemd-sysctl.service
If you still don’t observe changes, then you could be affected by a variation of what I posted in
https://forums.opensuse.org/english/get-technical-help-here/how-faq-forums/unreviewed-how-faq/486935-etc-sysctl-conf-not-read-boot-no-longer-usable.html
Although in the above thread sysctl on my machine started working after posting, it definitely had not been working for a long time beforehand. It’s unknown why it started working, it could have been an update pushed in the meantime or something “jiggled loose” and started working but I am pretty sure sysctl is not working in some undetermined number of machines.
If you feel ambitious, towards the end of my referenced thread, I posted a script that adds new IPv4 TCP/IP values which includes enlarging buffers and changing the Congestion Control Algorithm. If you run the script adding them to your sysctl, restart sysctl as I’ve described and still don’t see changes, then you should know that any other entries in your sysctl.conf likely aren’t being applied, also. Any modifications to sysctl.conf can be removed simply by deleting the new lines in the file.
TSU