Why Area 0 in OSPF is a Backbone Network?
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In OSPF, if there are more than 1 areas have to be configured always make area 0 as a backbone network, because while designing networks it is a best practice to start with area 0 and then expand it into other areas.
The basic concept behind this idea is that all areas are physically connected to area 0 and area 0 resides at the center of all other areas. Whatever routing information is generated is transferred into area 0 by other areas and then area0 spreads that information into other areas.
If we are unable to connect any area physically to area 0 (which is mandatory) we need to configure a Virtual Link between that area and area 0 provided they both should have a common area which is physically connected to both the areas.
Ex: consider there are 3 areas in ospf( area 0, area 1 and area 2). area 0 and area 1 are physically connected to each other and area 2 is physically connected to area 1 but unable to connect to area 0 in this situation we can configure a Virtual Link between area 0 and area 2.
