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Chapter 4
OSPF Areas
Enabling OSPF is common for all implementations of OSPF; the differ-
ence comes when you configure parameters to make OSPF behave in the
desired fashion. We'll cover parameters for NBMA as well.
The basic elements of OSPF configuration are:
Enabling OSPF
Configuring OSPF for different network types
Configuring the OSPF area
Route summarization
Route redistribution (covered in detail in Chapter 10, "Route
Optimization")
Interface parameters
We will start with basic configuration of OSPF, then introduce commands
relating to NBMA, as well as the methods and commands used to verify
proper configuration and operation of OSPF.
Discovering the Network with OSPF
The moment OSPF is enabled on a router and networks are added to the
OSPF process, the router will try to discover the OSPF neighbors on the con-
nected links. Here is a sample of what OSPF events transpire when the inter-
face is added to an OSPF process:
RouterA(config-router)#network 172.16.10.5 0.0.0.0 area 0
RouterA(config-router)#
OSPF: Interface Serial0 going Up
OSPF: Tried to build Router LSA within MinLSInterval
OSPF: Tried to build Router LSA within MinLSInterval^Z
RouterA#
OSPF: rcv. v:2 t:1 l:44 rid:172.16.20.1
aid:0.0.0.0 chk:3B91 aut:0 auk: from Serial0
OSPF: rcv. v:2 t:2 l:32 rid:172.16.20.1
aid:0.0.0.0 chk:2ECF aut:0 auk: from Serial0
OSPF: Rcv DBD from 172.16.20.1 on Serial0 seq 0x71A opt
0x2 flag 0x7 len 32 state INIT
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