For example, the IP segment of your LAN is192.168.1.0.
You do it strategically,
192.168.1.0 255.255.0 0.0 TCP 80 allowed.
The condition is set to strict! The port you want to open will be added to the policy.
192.168.1.0 255.255.0 0.0 TCP x where x is the port number.
If the router can be controlled, I suggest you call everyone to a meeting. There are many problems in LAN now!
It seems quite cool for me to use 8M by myself. I suggest you don't enjoy it, it will become more and more troublesome in the future.