OSPF metrics

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Oct 6th, 2008
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Hi all, can anyone tell me how ospf works out the best cost to a destination? what metrics does it use? If I have say 2 circuits to the same destination, 1 has 10 routers, all with 2 meg lines, the other router uses 3 routers to get there but with the same 2 meg bandwidth between them, would it load balance these circuits ?

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Giuseppe Larosa Mon, 10/06/2008 - 05:38
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Hello Carl,

the answer is no.

OSPF cost is calculates on each link on the path to destination as:

10^8 /Interface bandwidth in bps

10^8/2000000 = 50

the cumulate cost is the sum of all link costs to the destination:

path 1 : 10*50 + cost of lan interface

path2 : 3*50 + cost of lan interface

only path2 will be used because it is the shortest path to destination

Hope to help



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