When two routers attached to a network both attempt to become the designated router, the one with the highest router priority takes precedence. A router whose router priority is set to 0 is ineligible to become the designated router on the attached network. Router priority is specified per router interface and is advertised in hello packets sent out by the interface.
Use the ipv6 ospf priority command in interface configuration command mode to specify the router priority that will be included in LSAs going out this interface.
OSPF Designated Router Topology displays a designated router topology example. The example will configure the four displayed routers with the following priorities:
Router 4 will not take part in the election process at all. Router 3 has the highest priority and therefore will be elected DR. Router 1 has the second highest priority and will be elected BDR.