I have been trying to solve an issue where I have one router and one AP, both from Mikrotik. There are 2 networks in the wild with DHCP servers being set up in the router. The AP connected with a cable would need to work as a DHCP relay but on the same networks so it would allow a flawless roaming of clients on the move.
Please see this picture which should be way more descriptive.
https://www.flickr.com/photos/135869180@N05/21678865608/in/shares-B63f20/
Will be glad for help with this.