How do I setup a static route

On my DMZ I have a server running with docker containers. Docker uses the 172.x.x.x networks and my DMZ is specified to 192.168.20.x network.

I’ve tried to setup in /etc/config/network a static route like this:
config route
option interface ‘lan’
option netmask ‘255.255.0.0’
option gateway ‘192.168.20.5’
option metric ‘1’
option target ‘172.18.0.1’
But it does not route from my LAN to DMZ.

Do I need to setup firewall rules also?