HP 3500YL - Manual (Page 223)

IP Routing Features
Configuring OSPF
Priority is configurable by using the vlan < vid > ip ospf priority < 0-255 >
command at the interface level. You can use this parameter to help bias one
router as the DR. (For more on this command, refer to “Priority Per-Interface”
on page 5-83.) 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.
For example, in figure 5-20, the DR and BDR for 10.10.10.0 network in area 5
are determined as follows:
Router A Priority: 0 Cannot become a DR or BDR.
Router B Priority: 1 DR for the 10.10.10.0 network.
Router C Priority: 2 BDR for the 10.10.10.0 network.
Router D Priority: 0 Cannot become a DR or BDR.
Router E Priority: 3 Becomes the new BDR if router B becomes
unavailable and router C becomes the new DR.
Router “B”
Priority: 1
ID:10.10.10.2/24
ID:10.10.10.1/24
Priority 0
Area 5
Router “D”
Priority: 0
ID:10.10.10.4/24
Router “C”
Priority: 2
ID:10.10.10.3/24
Router “A”
ID:99.101.1.1/24
Area 0 (Backbone)
Router “X”
ID:99.101.1.2/24
Router “E”
Priority: 3
ID:10.10.10.4/24
Figure 5-20. Example of Designated Routers in an OSPF Area
To learn the router priority on an interface, use the show ip ospf interface
command and check the Pri setting under OSPF interface configuration.
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