OSPF ABR Type 3 LSA Filtering on Cisco IOS

Hello Chris

If you’ll notice, the L0 interface on R4 with an IP address of is in Area 0. This is not shown in the diagram with a colored ellipse, but is shown within the configuration of R4.

The Area 0 of an OSPF network can simply be applied to a single interface, even to a loopback interface, fulfilling the backbone area requirement of OSPF.

I hope this has been helpful!


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