Configuration Guide User guide

FastIron Configuration Guide 1229

53-1002494-01

OSPF overview

FIGURE 159 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 160.

NOTE

Priority is a configurable option at the interface level. You can use this parameter to help bias one

router as the DR.

FIGURE 160 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 976.

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.

Router A

Router B

Router C

priority 10

priority 20

priority 5

Designated Backup Router

Designated Router