I have a Prolink H5204 router. When I type 192.168.1.1, I can configure my router (as expected) but when I type my public internet IP address I can also configure my router.
So I want to stop this public accessing using my public internet IP address. Could you please tell me how can I do this please?
Disable WAN access under Advance - Remote Access:
I assume that you are referring to a browser (Firefox, Chrome, Internet Explorer etc) where you typed 192.168.1.1 and configured your router. There should be an option to disable remote management from the internet (not from local/internal network, it will disable your access to the router). I don't have this router on my network in order to tell you exactly where to find it but I'm positive that a switch should be there.
You need to open the router's home page (by the IP as you have done) and disable the "Web based Configuration". EDIT (As per Robert's Schmidt suggestion).
Sadly there is no online manual or documentation for your router so I can't give you more information.
Also, make sure your firmware is up to date.
Go to Advance -> ACL Config.
There you will see two Direction select: LAN and WAN. You may select "ANY" service for LAN allowing all features to be enabled for LAN Ethernet port but disable or untick all service under WAN.
Apply the setting.
