NBMA broadcast implementation

FIGURE 5 . 4 NBMA broadcast implementation
This configuration guarantees that all routers have connectivity and that all are able to participate
in the DR/BDR election process. Once the DR and BDR have been chosen, the meshed
networks act as a broadcast network. All LSA updates are sent to the DR and BDR, and the DR
floods the updates out every active OSPF interface.
One of the major weaknesses with this configuration is that if one of the PVCs fails (especially
if it is a PVC between a DROther and the DR), then communication is also halted between
the two adjacent peers, and the OSPF routing domain no longer functions properly.
It is also important to note that non-broadcast is the default network type on physical
NBMA interfaces. Remember, you are able to change the network type on any interface in an
OSPF process. In order to configure broadcast as the network type for an interface, you must
enter the ip ospf network broadcast command in interface configuration mode.