Configuring Multi-Area OSPF

Configuring Multi-Area OSPF
Let’s examine the syntax to configure OSPF on RouterA. First, we need to enable the OSPF process
on the router:
RouterA (config)#
router ospf 70
where
70
is the Process ID.
Next, we need to identify each of the networks connected to the router that we want to participate
in the OSPF process. The
network
statement will actually add interfaces that have an
IP address that falls within the range specified in the network statement. In this example, we
have two networks connected to RouterA (1.1.1.0/24 and 1.1.2.0/24):
RouterA(config-router)#
network 1.1.1.0 0.0.0.255 area 0
where
1.1.1.0 0.0.0.255
is the network and wildcard mask of a network connected to
RouterA and where
0
is the area that network 1.1.1.0/24 is a member of.
RouterA(config-router)#
network 1.1.2.0 0.0.0.255 area 0
Note that the previous two statements could be consolidated into a single statement, such as
the following, because both interfaces are members of the same area. The same goes for the two
statements shown later for RouterC.
RouterA(config-router)#
network 1.1.0.0 0.0.255.255 area 0
The syntax for RouterB is similar to that used for RouterA. The primary difference is that
RouterB is connected to two areas, for which individual
network
statements are necessary:
RouterB(config)#
router ospf 70
RouterB(config-router)#network 1.1.2.0 0.0.0.255 area 0
RouterB(config-router)#network 1.1.3.0 0.0.0.255 area 1
The syntax for RouterC is very similar to that of RouterA. The difference is that RouterA is
internal to Area 0, thereby classifying it as a backbone router:
RouterC(config)#router ospf 70
RouterC(config-router)#network 1.1.3.0 0.0.0.255 area 1
RouterC(config-router)#network 1.1.4.0 0.0.0.255 area 1