Last Updated on July 31, 2021 by Admin 1
Examine the following output of the show ip ospf interface command.
What would be the effect of executing the auto-cost reference bandwidth 2000 command on Router43 in router OSPF mode?
- the cost of the Serial interface would increase to 20
- the cost of the FastEthernet interfaces would increase to 2000
- the cost of the Serial interface would increase to 647
- the cost of the FastEthernet interfaces would increase to 20
Explanation:
If the auto-cost reference bandwidth 2000 command is executed in router OSPF mode it will result in a cost to the FastEthernet interfaces of 20. The formula for arriving at the cost is:reference bandwidth / interface bandwidth = costThe default reference bandwidth for FastEthernet is 100 Mbps. If the reference bandwidth is set at 2000 Mbps using the auto-cost reference command, and the FastEthernet interface has a bandwidth of 100 Mbps, the resulting cost is 20 (2000 / 100 = 20).The auto-cost reference bandwidth command is executed in router OSPF mode to affect all interfaces. Alternatively, the cost of each interface can be set separately with the ip ospf cost command issued in interface configuration mode. The two commands can also be used in combination: you can set all interfaces with the auto-cost reference bandwidth command, and then set a single interface to a different cost with the ip ospf cost command.The command would not result in the cost of the Serial interface increasing to 20 or to 647. With a reference bandwidth of 2000 Mbps and interface bandwidth of 1544 kbps (the default bandwidth of a serial interface), the resulting cost would be 1294.
If the auto-cost reference bandwidth 2000 command is executed in router OSPF mode it will result in a cost to the FastEthernet interfaces of 20. The formula for arriving at the cost is:reference bandwidth / interface bandwidth = costThe default reference bandwidth for FastEthernet is 100 Mbps. If the reference bandwidth is set at 2000 Mbps using the auto-cost reference command, and the FastEthernet interface has a bandwidth of 100 Mbps, the resulting cost is 20 (2000 / 100 = 20).The auto-cost reference bandwidth command is executed in router OSPF mode to affect all interfaces. Alternatively, the cost of each interface can be set separately with the ip ospf cost command issued in interface configuration mode. The two commands can also be used in combination: you can set all interfaces with the auto-cost reference bandwidth command, and then set a single interface to a different cost with the ip ospf cost command.The command would not result in the cost of the Serial interface increasing to 20 or to 647. With a reference bandwidth of 2000 Mbps and interface bandwidth of 1544 kbps (the default bandwidth of a serial interface), the resulting cost would be 1294.
Objective:
Layer 3 Technologies
Sub-Objective:
Configure and verify OSPF path preference
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