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Cisco IOS Cookbook, 2nd Edition by Ian Brown, Kevin Dooley

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Configuring OSPF

Problem

You want to run OSPF on a simple network.

Solution

You can enable OSPF on router by defining an OSPF process and assigning an address range to an area as follows:

Router5#configure terminal 
Enter configuration commands, one per line.  End with CNTL/Z.
Router5(config)#router ospf 87
Router5(config-router)#network 0.0.0.0 255.255.255.255 area 0
Router5(config-router)#exit
Router5(config)#end
Router5#

Discussion

The first line in this configuration example defines the OSPF process:

Router5(config)#router ospf 87

The OSPF process number (87) doesn’t propagate outside of the router. So you can use a different value for every router in an AS. Note that this is different from EIGRP, where every router in the AS must have the same process number. The process number can take any value between 1 and 65,535.

The network statement in this example then takes the simplest possible approach to defining areas by putting every interface on the router into area 0:

Router5(config-router)#network0.0.0.0 255.255.255.255 area 0

The first two arguments of the network statement are an IP address and a corresponding set of wildcard bits. In this case, 0.0.0.0 255.255.255.255 matches every possible IP address. So every interface on this router is assigned to area 0.

In this case, we have defined the area by using a single number. You can define area numbers to be anything between 0 and 4,294,967,295. You can also use dotted decimal notation for areas, in which case you would write area 0 as ...

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