Which protocol and ports do D-Link DWS-302x and DWS-4026 series switches use to communicate with and manage their AP's?

It uses the DWAPP (D-Link Wireless AP Protocol). It can cross a L2 or L3 network but must meet the following conditions: 

 

1) No NAT between the wireless controller and the AP's. However, a VPN can be used if the AP's are across the internet

 

2) VLAN (L2) and routing (L3) must be configured between the controller and the AP's

 

3) The following ports must be opened between the wireless controller and the AP's (you will need to allow them in any filter or firewall between the switch and AP's):

 

Between the controller and the AP's: 

 

 

Between one controller and another controller (cluster group):