Brocade Virtual ADX Switch and Router Guide (Supporting ADX v03.1.00) - Manual (Page 117)

Brocade Virtual ADX Switch and Router Guide 103
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Overview of OSPF
6
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 20
FIGURE 20 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 21 .
NOTE
Priority is a configurable option at the interface level. You can use this parameter to help bias one
router as the DR.
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 router ID is the IP address configured on the lowest numbered loopback
interface. If the Layer 3 Switch does not have a loopback interface, the default router ID is the lowest
numbered IP address configured on the device. For more information or to change the router ID,
refer to
“Changing the router ID” on page 61.