OSPF best route selection

First ospf process compares the ospf route type

The intra-area route (type1 and type2) is better than inter-area route (type 3),   inter-area route is better than external route (type 5).   Type 5 is better than type 7

So preferred route sequence is below

O (intra-area) >  OIA (inter-area) > E1 (external 1)> E2 (external 2) >NS1 (type 7) > NS2 (type 7)

If the ospf route type is same, than the ospf process compares the metric, whose metric low, who will be the ospf best route. if the routes metric are same,  all those routes are selected as the best route. 

How many equal cost routes can be selected as the best routes is depend on the platform and the command  “maximum-paths X” under the router ospf  configuration.

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