From the course: Cisco CCNP ENARSI v1.1 (300-410) Cert Prep: 2 VPN Technologies

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OSPF metric calculation

OSPF metric calculation

From the course: Cisco CCNP ENARSI v1.1 (300-410) Cert Prep: 2 VPN Technologies

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OSPF metric calculation

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- [Instructor] In this video, we want to take a look at how OSPF calculates its metric or its cost. Now, with EIGRP, recall that by default, we considered bandwidth and delay. However, OSPF is purely basing its metric, its cost, on bandwidth. And here's the formula. The cost equals a reference bandwidth divided by an interface bandwidth, and by default, the reference bandwidth is 100 million bits per second. In other words, 100 megabits per second. So in this example, if we want to go from PC1 to PC2, let's calculate the cost going at the two different paths we have available to us. For that link between R1 and R2, we see that that's a 100 meg link, so the cost is the reference bandwidth of 100 meg divided the link speed of 100 meg, and that equals one. Similarly, the cost from R2 to R3, that's a 100 meg link. So that's got a cost of one, and the cost going out of R3 down to PC2, that's got a cost of one. But take a look at that 10 megabit per second link between R1 and R3. That's a…

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