Backup Designated Router (BDR)

The backup to an OSPF network’s Designated Router (DR).

A router in an OSPF Broadcast-type network is elected Designated Router (DR) and another is elected Backup Designated Router (BDR). These two routers serve as the central points for exchanging OSPF routing information. All other OSPF-enabled routers will synchronize their LSDBs from the DR and BDR, and will only form full adjacencies with the DR and BDR.

The BDR will become the DR if the DR is disabled or otherwise becomes unreachable.