OSPF Terminology
BMA: e.g. Ethernet, allow multiple access and provide broadcast ability. A DR and BDR must be elected for BMA networks.
Point-to-Point: comprises a unique NBMA configuration, eliminating the need for DR’s and BDR’s.
Router ID: is an IP address used to identify the router. Cisco chooses the Router ID by using the highest IP of all configured loopback interfaces. If no loopback interfaces are configured, OSPF will choose the highest IP of all configured interfaces on the router.