Question : Why all other areas must be connected to ospf area 0(backbone)?

What I have read and know till now is since ospf behaves like distance vector protocol for inter area communication hence it is vulnerable to routing loops that’s why all the ABRs must be connected to ospf area0 and interarea communication happens through backbone area ….but you may ask that how distance vector in inter area communication ??The answer is ABR is the only router which propagates interarea routes within the area that means unlike the behaviour of distance vector where all the router must have the complete topology in link state router in a particular area would not know about the topology of another area and for interarea information routers just rely on ABR just like DUAL where router believes on its neighbor for the other routes in the network ….. since anything which is not resolved by you and advertised by the neighbor may or may not be correct hence here link state wins ….. Now consider a situation where I have 10 areas connected adjacent and something goes wrong in area 10 now to propagate the update till area 1 through all the way 10 to 1 will take considerable amount of time and the update may not reach correctly …now a situation where my ABRs are connected to area 0 now they can easily send the route another ABR through area 0 , just one backbone area to cross ….vulnerability is considerably minimized.


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