On both broadcast and NBMA networks, you can set the DR priority of OSPF interfaces to impact the DR/BDR election. In common cases, the router with high performance and reliability is selected as the DR/BDR.
On broadcast and NBMA networks, if the neighbor relationship is established between every two routers, a large number of unnecessary LSAs are generated on the networks, thus severely affecting network performance.
To avoid this problem, you can elect specified routers respectively as the Designated Router (DR) and Backup Designated Router (BDR). The other routers on the network are called DROthers.
The following functions are implemented through DR/BDR election:
A DROther only establishes neighbor relationships with the DR and BDR, and sends data-updating packets to the DR and BDR in multicast mode.
The DR spreads the data-updating packets to the DROther in multicast mode.
When the DR is faulty, the BDR takes over the DR functions and acts as a new DR.
For a broadcast or an NBMA network, you can set the DR priority of the interface to impact the DR/BDR election.
interface interface-type interface-number
ospfv3 dr-priority priority [ instance instance-id ]
By default, the DR priority of the interface is set to 1.
The DR priority of a router interface affects the qualification of the interface for the election of the DR. The router whose priority is 0 is not elected as the DR or BDR.
After the DR priority is changed, you can re-elect a DR or BDR through the following methods, which, however, will result in the interruption of the OSPFv3 neighbor relationship between routers and therefore are used only when necessary.