If you, like me have TP-Link WR1043ND with DDWRT on it and after assigning a wan port to switch realized that it’s not working just go to:
Administration, Commands and paste the code below in the text field:
swconfig dev rtl8366rb vlan 1 set ports ‘0 1 2 3 4 5t’
Hit the “Save startup” button
And now restart your router for the changes to take effect and your’re done!
Solution found searching DDWRT forum.