Brocade FastIron Ethernet Switch Layer 3 Routing Configuration Guide - Manual (Page 248)

FIGURE 21 Backup designated router becomes designated router
If two neighbors share the same priority, the router with the highest router ID is designated as the DR.
The router with the next highest router ID is designated as the BDR.
NOTE
By default, the Brocade device’s router ID is the IP address configured on the lowest numbered
loopback interface. If the device does not have a loopback interface, the default router ID is the lowest
numbered IP address configured on the device.
When multiple routers on the same network are declaring themselves as DRs, then both priority and
router ID are used to select the designated router and backup designated routers.
When only one router on the 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.
The DR and BDR election process is performed when one of the following events occurs:
• an interface is in a waiting state and the wait time expires
• an interface is in a waiting state and a hello packet is received that addresses the BDR
• a change in the neighbor state occurs, such as:
‐ a neighbor state transitions from ATTEMPT state to a higher state
‐ communication to a neighbor is lost
‐ a neighbor declares itself to be the DR or BDR for the first time
OSPFv2
248 FastIron Ethernet Switch Layer 3 Routing Configuration Guide
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