Adding OSPF routes to the routing table

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May 24th, 2008
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When OSPF has two paths to a destination subnet and is deciding upon which route to add to the routing table it calculates the cost of each route by dividing 100 Mbps by the outgoing interface bandwidth. It then adds up all the costs - which path does it choose the highest numeric cost calculated or the lowest?

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lamav Sat, 05/24/2008 - 19:31
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Lowest.


Imagine a link with a bandwidth capability of 100 Mbps. Using the formula of 10^8/interface bandwidth (BW), the metric cost would be 100,000,000/100 Mbps = 1. A slower link with a bandwidth capability of 10 Mbps (which you know is not as good a path to take as the 100 Mbps) would have a cost metric of 10. So, as you can see a higher cost metric means it's a less attractive route.


Victor



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