Port forwarding enables SSH access to my Raspberry Pi home server from outside the home by forwarding traffic directed at a port on the router (reachable over the Internet by dynamic DDNS) to the SSH port on the internal server behind a NAT firewall.
OpenWrt port forward configuration is done in /etc/config/firewall. A sample entry that redirects port 55555 on the router to the SSH server listening on port 22 at 192.168.1.88:
config 'redirect' option 'name' 'ssh' option 'src' 'wan' option 'proto' 'tcpudp' option 'src_dport' '55555' option 'dest_ip' '192.168.1.88' option 'dest_port' '22' option 'target' 'DNAT' option 'dest' 'lan'
Save and make the changes active by running:
# /etc/init.d/firewall restart
Alternative: setup port forwarding in LuCI under Network->Firewall->Port Forwards.
Example: SSH login outside the home enter ssh -p 55555 my.external.ip.address and the connection will be forwarded to the Pi server.
Source: OpenWrt Port Forwarding