When there are multiple routes available to the same network with different route types, routers use this order of preference (from highest to lowest):1.Intra-area routes.2.Inter-area routes.3.External Type-1 routes.4.External Type-2 routes.
If there are multiple routes to a network with the same route type, the OSPF metric calculated as cost based on the bandwidth is used for selecting the best route. The route with the lowest value for cost is chosen as the best route.
If there are multiple routes to a network with the same route type and cost, it chooses all the routes to be installed in the routing table, and the router does equal cost load balancing across multiple paths.
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This is always a confusing topic at some point when we are learning it. I have this very useful link with some examples and how cost will be taken into account when selecting routes, also it is included the rules for inter-area (different areas) or intra-area (same area) route selection, it basically depends on where the destination is located and the type of LSA for that prefix.
> intra area - a route to a subnet or network inside the same area as the router. LSA type 1 and 2 fall in here / router and network LSAs
> inter area - a route to a subnet in an area of which the router is not a part. LSA tpe 3 falls in here / summary LSAs
I hope this link helps you understanding more this behavior: