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Chapter 4
OSPF Areas
We used the OSPF debugging commands to produce this output. The con-
figuration commands consisted of two simple OSPF commands:
router ospf 1
This command starts the OSPF process on RouterA.
The number 1 indicates the OSPF process ID.
network area 0
This command adds the net-
work (link) The wildcard mask indicates that only this single IP
address is going to be part of the link. Area 0 indicates that the interface
with the address is assigned to Area 0.
The generic IOS syntax for the commands is router ospf process-id
and network ip-address wildcard-mask area area-id, respectively.
Since the link described by the previous output is point-to-point, no DR/
BDR election occurred; instead, each router decided which would be the
Master and which would be the Slave. Once the Master/Slave roles had been
established, DBD packets containing LSA information for each router were
LSA exchanges continue until the link-state databases for each router are
identical (synchronized). Once that happens, the OSPF state changes to Full.
Discovering the neighbors on a broadcast network is done somewhat differ-
ently. Here you will see what happens on a broadcast multi-access network:
RouterA(config-if)#router ospf 1
area 0
OSPF: Interface Ethernet0 going Up
OSPF: Tried to build Router LSA within MinLSInterval
OSPF: Tried to build Router LSA within MinLSInterval
OSPF: end of Wait on interface Ethernet0
OSPF: DR/BDR election on Ethernet0
OSPF: Elect DR
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