IPv6 Configuration Guide K/KA/KB.15.15

• Router C Priority: 2 BDR for the 2001:db8:0:5::/64 network.
• Router D Priority: 0 Cannot become a DR or BDR.
• Router E Priority: 1 Becomes the new BDR if router B becomes unavailable and router C
becomes the new DR.
Figure 25 Example of designated routers in an OSPFv3 area
Router "B"
2001:db8:0:5::10:2/64
ID:10.1.1.2
Priority: 3
2001:db8:0:5::10:1/64
ID:10.1.1.1
Priority 0
Area 5
Router "D"
2001:db8:0:5::10:5/64
ID:10.1.1.5
Priority: 0
Router "C"
2001:db8:0:5::10:3/64
ID:10.1.1.3
Priority: 2
Router "A"
2001:db8:0::1:1/64
ID: 9.1.1.1
Area 0 (Backbone)
Router "X"
2001:db8:0::1:2/64
ID: 9.1.1.2
Router "E"
2001:db8:0:5::10:4/64
ID:10.1.1.4
Priority: 1
To verify the router priority on an interface, use the show ipv6 ospf3 interface command
and check the Pri field.
NOTE: Once a DR is elected, the DR and BDR status do not change if a higher-priority router
joins the network, unless the DR or BDR goes down.
By default, the router IDis typically the lowest-numbered IPv4 loopback address or the
lowest-numbered (user-configured) loopback interface configured on the device.
If multiple networks exist in the same OSPFv3 area, the recommended approach is to ensure that
each network uses a different router as its DR. Otherwise, if a router is a DR for more than one
network, latency in the router could increase because of the increased traffic load resulting from
multiple DR assignments.
When only one router on an OSPFv3 network claims the DR role despite neighboring routers with
higher priorities or router IDs, this router remains the DR. This is also true for BDRs.
OSPFv3 router types 251