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In OSPF (Open Shortest Path First), the reference bandwidth is a value used to calculate the OSPF cost of a link. The cost is calculated using the formula:

Cost = Reference Bandwidth / Interface Bandwidth

To achieve a specific metric, such as a cost of 10 for a 1-Gbps link, you can set the reference bandwidth accordingly.

Given that the interface bandwidth is 1 Gbps (which is equivalent to 1,000,000,000 bits per second), if you want the cost to equal 10, you can manipulate the reference bandwidth as follows:

Setting the reference bandwidth to 10,000,000,000 (which is 10 Gbps) allows the OSPF cost calculation to proceed as follows:

Cost = 10,000,000,000 / 1,000,000,000 = 10

This results in the desired OSPF metric of 10 for the 1-Gbps link. Hence, the correct setting of the reference bandwidth for achieving a metric of 10 for a 1-Gbps link is indeed 10,000,000,000.