OpenWRT: How to forward all system ports from LAN to outside (something like DMZ)

Question

Computer networks

There are several computers on the LAN. All are connected to a router (OpenWRT), and access the Internet through it.
The IP address is dynamic.
One computer works as a NAS and as a web server, FTP-server ... Here it must be made available from the Internet.
There is a diagram of the router here:
wiki.openwrt.org/toh/buffalo/wzr-hp-g300h

There are instructions on how to allocate a port for DMZ, but all instructions create new VLANs and block access between the LAN and the DMZ device. In general, this is the real DMZ.

And I want all computers to be on the same LAN, and freely communicate with each other.

I kind of figured out that you need to use iptables for this, but I just can’t figure out the syntax.

Well, as the second part of this task - it would be necessary to access this computer both from the local area and from the Internet at the same address, but this can probably be done through DNSMASQ, and I will finish it myself.

Answer 1

Ok, it worked.
How to do it found here:
www.youtube.com/watch?v=IqgSL884lBU
It turns out that on OpenWRT this is done through the GUI:
Network -> Firewall -> Redirections:

Answer 2

isn't it habrahabr.ru/qa/853/#answer_4297 ?