# How Is the Cost of an OSPF Interface Calculated?

Latest reply: Sep 18, 2015 07:12:26 1288 2 0 0

# How Is the Cost of an OSPF Interface Calculated?

The principles of calculating the cost of an OSPF interface are as follows: The cost configured on the interface is preferred. If no cost is configured on the interface, the formula for calculating the cost of the interface is as follows: Cost = Reference bandwidth/Interface bandwidth. The default reference bandwidth of OSPF is 100 Mbit/s.

For example, the cost of a 10 Mbit/s Ethernet interface = 100 Mbits per second/10 Mbits per second = 10. If the calculation result is smaller than 1, the cost is set to 1. For example, the cost of a GE interface is 100 Mbits per second/1000 Mbits per second = 0.1, which is less than 1. Therefore, the cost of this interface is 1.

The default cost on the loopback interface, which is a virtual interface, is 0.

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 h00222394 Created Sep 18, 2015 06:08:16 Helpful(0) Helpful(0) .pcb{margin-right:0} .pcb table{table-layout:auto;} div#jdc_suspicious_threads{ background: #fcf5d8; text-align: center; font-size: 12px; } If there are many verder in the network, we suggest you adjust to the same value. Because different vender have the different default value. x convention：
 MagicKnight Created Sep 18, 2015 07:12:26 Helpful(0) Helpful(0) .pcb table{table-layout:auto;} div#jdc_suspicious_threads{ background: #fcf5d8; text-align: center; font-size: 12px; } If we could get the command that how to change the default cost computing method, may be better. x convention：

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