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Explain the OSPF, Open Shortest Path First. What are the different areas in OSPF?OSPF is a protocol for routing to be used in IP networks. It is a link-state routing protocol and is a part of interior gateway protocols group. It operates in a single autonomous system. OSPF is most widely used interior gateway protocol.
The areas are as follows:
Backbone area
Backbone is also referred as ‘area 0’ or ‘area 0.0.0.0’. It is the core of an OSPF network and all other areas are connected to it. Inter-area routing happens through routers that are connected to the backbone area and their associated areas.
Stub area
The external route advertisements are not received by the stub area. Many route advertisements are configured into an area. This occurs at the time where the routing table consists of mostly external routes. It is advised to have a default route to the stub area. Stub area will have only one OSPF router.
Not-so-stubby area
A stub area which can import autonomous system external routes and send them to other areas is known as Not-so-stubby area. NSSA is an extension of stub area which allows external routes injection in a limited fashion into the stub area.
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