OSPF DR and BDR Election | Part 1
OSPF DR and BDR Election | Part 1
DR and BDR election is done via the Hello protocol.
Hello packets are exchanged via IP multicast packets on each segment.
The router with the highest OSPF priority on a segment will become the DR for that segment.
The same process is repeated for the BDR. In case of a tie, the router with the highest RID will win.
The default for the interface OSPF priority is one. Remember that the DR and BDR concepts are per multi-access segment.
Setting the ospf priority on an interface is done using the ip ospf priority (value) interface command.
A priority value of zero indicates an interface which is not to be elected as DR or BDR.
The state of the interface with priority zero will be DROTHER.
CONFIGURE:
R1:
conf t
interface gi0/1
no shut
ip address 10.10.123.1 255.255.255.0
ip ospf priority 100
!
router ospf 1
network 10.10.123.0 0.0.0.255 area 0
end
wr
R2:
conf t
interface gi0/2
no shut
ip address 10.10.123.2 255.255.255.0
!
router ospf 1
no shut
network 10.10.123.0 0.0.0.255 area 0
end
wr
R3:
conf t
interface gi0/3
no shut
ip address 10.10.123.3 255.255.255.0
!
router ospf 1
network 10.10.123.0 0.0.0.255 area 0
end
wr
VERIFY:
show ip ospf neighbor
show ip ospf interface g0/1
clear ip ospf process
REFERENCES:
OSPF Design Guide
https://www.cisco.com/c/en/us/support...
Designated & Backup Designated Router
https://study-ccna.com/designated-bac....
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