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Chapter 4
OSPF Areas
It is also important to recognize that this command displays OSPF neigh-
bors and not adjacencies. To learn adjacency formations, study the following
summarization:
Point-to-point valid neighbors form adjacencies.
NBMA neighbors require special configuration (e.g., point-to-point
subinterfaces) for adjacency formation.
Broadcast multi-access neighbors require the election of a DR and a
BDR. All other routers form adjacencies with only the DR and BDR.
DR and BDR Election Procedure
Each OSPF interface (multi-access only) possesses a configurable Router Pri-
ority. The Cisco default is 1. If you don't want a router interface to partici-
pate in the DR/BDR election, set the Priority to 0 using the ip ospf
priority
command in Interface Configuration mode. Here is a sample (the
Priority field is bolded for ease of identification):
RouterA>show ip ospf interface
FastEthernet0/0 is up, line protocol is up
Internet Address 172.16.22.14/24, Area 0
Process ID 100, Router ID 172.16.246.1, Network Type
BROADCAST, Cost: 1
Transmit Delay is 1 sec, State BDR, Priority 1
Designated Router (ID) 172.16.247.1, Interface address
172.16.22.9
Backup Designated router (ID) 172.16.246.1, Interface
address 172.16.22.14
Timer intervals configured, Hello 10, Dead 40, Wait 40,
Retransmit 5
Hello due in 00:00:08
Neighbor Count is 2, Adjacent neighbor count is 2
Adjacent with neighbor 172.16.22.101
Adjacent with neighbor 172.16.247.1 (Designated
Router)
Suppress hello for 0 neighbor(s)
Message digest authentication enabled
Youngest key id is 10
RouterA>
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