Which router page are you looking at? Is it the Network Services Filter? That is for blocking outgoing connections, not incoming connections.I have a port forwarding service to port 8123.
I want to block the access to this port from a whole bunch of IPs. If you have firewall enabled is deny list. So if you do not have anything there everything is allowed. So, everybody can access my service 8123 port. If I add a certain host then this IP cannot access this from the outside.

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