Block DHCP on certain LAN Ports

I have two DrayTeks, a 3900 and a 2960.

They are connected by LAN ports but have a different LAN subnet and gateway.

Can I limit the DHCP server to a single LAN port, or can I block the DHCP requests/responses from that LAN port on each router?

DHCP will not venture onto another LAN as it would not be routable.

You should use RIP to connect them or make one a VLAN that is a member of the subnet of the other subnet so that they can communicate.

Otherwise you would have to overlap the subnets in which case it would be worth making just one the DHCP router, and all LAN traffic would route between both.

Best option would be to have one router and connect the switches via fibre or similar.