How to set an interface as the OSPF DR?
 

Configure SW1 to be the OSPF DR in the respective LAN .

Re: OSPF DR Election
 

Knowledge Points:
In the multi-access network environment, OSPF elects DR and BDR based on

• The OSPF interface priority

(config-if)#ip ospf priority [0-255]
The router with the highest priority will be the DR. If the value sets to 0, this interface will never be DR.

• If the interfaces are with the same priority, the router with the highest Router-ID will be selected as DR.

In this case, lower R1 and R6's interface priority and increase SW1’s interface priority to make SW1 be the DR.