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In contrast to a broadcast network where some OSPF protocol packets are multicast (sent to AllSPFRouters and AllDRouters), NBMA packets are replicated and sent to each neighboring router, in turn, as unicast. NBMA networks drop all OSPF packets with destination address AllSPFRouters and AllDRouters. Because the NBMA network does not broadcast, you must manually configure a list of neighbors and their priorities for all routers in the network eligible to become the DR (those with a positive, non-zero router priority). Before you begin this configuration, you should identify the following:
Once you have gathered the above information, you can configure the interfaces, and add neighbors for each interface that is eligible to become the DR (those with a positive, non-zero router priority).