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Consider a network that mixes link bandwidths from 128 kb/s to 40 Gb/s. Which value should be set for the OSPF reference bandwidth?
Correct Answer: C
Explanation/Reference: Explanation: Unlike the metric in RIP which is determined by hop count and EIGRP's crazy mathematical formulated metric, OSPF is a little more simple. The default formula to calculate the cost for the OSPF metric is (10^8/BW). By default the metrics reference cost is 100Mbps, so any link that is 100Mbps will have a metric of 1. a T1 interface will have a metric of 64 so in this case if a router is trying to get to a FastEthernet network on a router that is through a T1 the metric would be 65 (64 +1). You do however have the ability to statically specify a metric on a per interface basis by using the ip ospf cost # where the cost is an integer between 1-65535. So the big question is why would you want to statically configure a metric? The biggest advantage of statically configuring an OSPF metric on an interface is to manipulate which route will be chosen dynamically via OSPF. In a nut shell it's like statically configuring a dynamic protocol to use a specific route. It should also be used when the interface bandwidths vary greatly (some very low bandwidth interfaces and some very high speed interfaces on the same router).