Resetted cable modem to do some experiments to see if cable modem would then be accessable via special ips, but not accessable.

Then proceeded to do some testing with this tool:

https://hackertarget.com/udp-port-scan/

For example this tool will send some UDP packets to port 69 and this was received just fine on my computer even with firewall up.

Perhaps resetting cable modem might have had some effect.

Still need to test tcp/ip with somebody who is not behind NAT and has a good internet connection setup.

* Little update on cable modem situation *:

Network engineer replaced coax/green cable wall socket, noise from TV is now gone, pretty cool.

Still can't enter cable modem menu, but thats's ok for now, not required.