Understand Open Shortest Path First (ospf) Design Guide

Neighbor Count is 3, Adjacent neighbor count is 3
Adjacent with neighbor 203.0.113.41 (Backup Designated Router)
RTD#show ip ospf interface e0
Ethernet0 is up, line protocol is up
Internet Address 203.0.113.144 255.255.255.0, Area 0.0.0.0
Process ID 10, Router ID 192.0.2.174, Network Type BROADCAST
, Cost:
10
Transmit Delay is 1 sec, State DROTHER, Priority 1
Designated Router (ID) 203.0.113.151, Interface address 203.0.113.142
Backup Designated router (ID) 203.0.113.41, Interface address
203.0.113.141
Timer intervals configured, Hello 10, Dead 40, Wait 40, Retransmit 5
Hello due in 0:00:03
Neighbor Count is 3, Adjacent neighbor count is 2
Adjacent with neighbor 203.0.113.151 (Designated Router)

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Adjacent with neighbor 203.0.113.41 (Backup Designated Router)
RTB#show ip ospf interface e0
Ethernet0 is up, line protocol is up
Internet Address 203.0.113.143 255.255.255.0, Area 0.0.0.0
Process ID 10, Router ID 203.0.113.121, Network Type BROADCAST
, Cost: 10
Transmit Delay is 1 sec, State DROTHER, Priority 1
Designated Router (ID) 203.0.113.151, Interface address 203.0.113.142
Backup Designated router (ID) 203.0.113.41, Interface address
203.0.113.141
Timer intervals configured, Hello 10, Dead 40, Wait 40, Retransmit 5
Hello due in 0:00:03
Neighbor Count is 3, Adjacent neighbor count is 2
Adjacent with neighbor 203.0.113.151 (Designated Router)
Adjacent with neighbor 203.0.113.41 (Backup Designated Router)
This output shows very important information. At RTA output, Ethernet0 is in area 0.0.0.0. The
process ID is 10 (router ospf 10) and the router ID is 203.0.113.41.
Remember that the RID is the highest IP address on the box or the loopback interface, calculated
at boot time or whenever the OSPF process is restarted.
The state of the interface is BDR. Since all routers have the same OSPF priority on Ethernet 0
(default is 1), the RTF interface was elected as DR because of the higher RID.
In the same way, RTA was elected as BDR. RTD and RTB are neither a DR or BDR and their
state is DROTHER.
Take notice of the neighbor count and the adjacent count. RTD has three neighbors and is
adjacent to two of them, the DR and the BDR. RTF has three neighbors and is adjacent to all of
them because it is the DR.
The information about the network type is important and determines the state of the interface. On
broadcast networks such as Ethernet, the election of the DR and BDR are irrelevant to the end
user.
It does not matter who the DR or BDR are. In other cases, such as NBMA media such as Frame
Relay and X.25, this becomes very important for OSPF to function correctly.
With the introduction of point-to-point and point-to-multipoint subinterfaces, DR election is no
longer an issue. OSPF over NBMA is discussed in the next section.
Another command we need to look at is: