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JUNOS Cookbook by Aviva Garrett

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12.5. Configuring a Multiarea OSPF Network

Problem

Your OSPF network has a number of physical and departmental boundaries, and, for administrative purposes and for scalability, you want to divide the network into a number of areas.

Solution

Configure a second OSPF area on the router:

	[edit protocols]
	aviva@RouterG# set ospf area 0.0.0.1 interface fe-1/0/0.0

Discussion

To create additional areas in the OSPF network, configure the second area on the router's interface (or interfaces) that connects to the second area. In this recipe, we configure the second area, Area 0.0.0.1, on our router. This router acts as the ABR between the backbone area and Area 0.0.0.1. See Figure 12-2.

OSPF two-area topology

Figure 12-2. OSPF two-area topology

Check that the interface is configured:

	aviva@RouterG> show ospf interface
	Interface              State     Area       DR ID        BDR ID       Nbrs
	fe-0/0/1.0             DR      0.0.0.0     192.168.19.1 192.168.18.1     1
	fe-1/0/1.0             BDR     0.0.0.0     192.168.17.1 192.168.19.1     1
	fe-1/0/0.0             BDR     0.0.0.1     192.168.42.1 192.168.19.1     1

You see that interface fe-1/0/0 is up and is in Area 0.0.0.1.

Again, check that the neighbor is active:

	aviva@RouterG>  
show ospf neighbor detail Address Interface State ID Pri Dead 10.0.1.1 fe-0/0/1.0 Full 192.168.18.1 128 33 area 0.0.0.0, opt 0x42, DR 10.0.1.2, BDR 10.0.1.1 Up 01:11:30, adjacent 01:11:30 10.0.0.2 fe-1/0/1.0 Full 192.168.17.1 128 39 area 0.0.0.0, opt 0x42, DR 10.0.0.1, BDR 10.0.0.2 Up 01:11:30, adjacent ...

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