PC cannot telnet to OpenWrt device solution

A scene:
PC Direct-attached openwrt equipment, you can telnet through each other;
But when both are connected to the router, the PC cannot telnet to the OPENWRT device, and the OPENWRT device can telnet to the PC. As shown in figure:

Solution:
You need to add port mappings to the OPENWRT system to map the Telnet service in the intranet. Modify/etc/config/firewall to increase:

Config redirect
        option src              wan
        option src_dport        22002
        option dest             LAN
        option Dest_port
        option Proto            TCP

If you want to know more, you can read the/etc/config/firewall file carefully.
For more details, refer to:
[1] OpenWrt Port Forwarding
[2] OpenWrt How to configure a firewall