Brocade Multi-Service IronWare Routing Configuration Guide (Supporting R05.6.00) - Manual (Page 187)

Multi-Service IronWare Routing Configuration Guide 159
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OSPF point-to-point links
Designated router election in multi-access networks
In a network with no designated router and no backup designated router, the neighboring router
with the highest priority is elected as the DR, and the router with the next largest priority is elected
as the BDR, as shown in
Figure 9
FIGURE 9 Designated and backup router election
If the DR goes off-line, the BDR automatically becomes the DR. The router with the next highest
priority becomes the new BDR. This process is shown in
Figure 10 .
NOTE
Priority is a configurable option at the interface level. You can use this parameter to help bias one
router as the DR.
FIGURE 10 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.