CCNP ROUTE: 9.OSPF packets and database exchange process - Exchange with a DR

The big difference is the overriding choice of with whom each router chooses to perform database exchange.
Non-DR routers do not exchange their databases directly with all neighbors on a subnet.
Instead, they exchange their database with the DR. Then, the DR exchanges any new/changed LSAs with the rest of the OSPF routers in the subnet.

The non-DR performs database exchange with the same messages, but sends these messages to the 224.0.0.6 All-DR-routers (DR and BDR) multicast address.
The DR performs database exchange with the same messages but sends the messages to the 224.0.0.5 all-SPF-routers multicast address.

Because the process does not make DROther routers perform database exchange with each other, the routers do not reach the FULL neighbor state, remaining in 2-Way state.
DROthers form FULL neighborships only with the DR and BDR on a LAN segment.

Consider the LAN connecting R1, R2 and R3 routers. Shutting down R3 and reloading R1 and R2, the DR/BDR election process chooses R2 as DR and R1 as BDR:
When powering up R3, it joins the network as DROther, because the DR/BDR are already chosen, even if R3 now has the highest RID.

R2#show ip ospf neighbor 

Neighbor ID     Pri   State           Dead Time   Address         Interface
1.1.1.1           1   FULL/BDR        00:00:36    192.168.0.1     FastEthernet0/0
3.3.3.3           1   FULL/DROTHER    00:00:32    192.168.0.3     FastEthernet0/0
13.13.13.13       1   FULL/DR         00:00:39    192.168.168.2   FastEthernet0/1

R3#show ip ospf neighbor 

Neighbor ID     Pri   State           Dead Time   Address         Interface
1.1.1.1           1   FULL/BDR        00:00:30    192.168.0.1     FastEthernet0/0
2.2.2.2           1   FULL/DR         00:00:39    192.168.0.2     FastEthernet0/0

R3 exchange messages with both DR and BDR using 224.0.0.6 and receives replies from both R1 and R2 using the destination address 224.0.0.5:

R3#debug ip packet
*Mar  1 00:20:42.495: IP: s=192.168.0.3 (local), d=224.0.0.6 (FastEthernet0/0), len 96, sending broad/multicast
*Mar  1 00:20:42.527: IP: s=192.168.0.2 (FastEthernet0/0), d=224.0.0.5, len 96, rcvd 0

*Mar  1 00:20:44.495: IP: s=192.168.0.3 (local), d=224.0.0.6 (FastEthernet0/0), len 84, sending broad/multicast
*Mar  1 00:20:44.595: IP: s=192.168.0.1 (FastEthernet0/0), d=224.0.0.5, len 104, rcvd 0

Note: Although OSPF does not send routing updates on a periodic interval, as do distance vector protocols, OSPF does reflood each LSA every 30 minutes.