Command
Auto-Cost Reference-Bandwidth
Use
Changes how OSPF calculates its metric. By default, a FastEthernet and above will have a cost of 1, so a gigabit interface will be equal with a fastethernet. This is not ideal.
Syntax
Router(config-router)#auto-cost reference-bandwidth <bandwidth>
Example
In this example, we will configure OSPF to have a reference bandwidth of 10000 Mbs. This means that a 10 Gbps interface would have cost of 1.
R2(config)#router ospf 1 R2(config-router)#auto-cost reference-bandwidth 10000
Notice that fa0/0 now has a cost of 101.
R2(config-if)#do show ip route ospf 1.0.0.0/32 is subnetted, 3 subnets O 1.1.1.1 [110/101] via 10.1.1.1, 00:00:01, FastEthernet0/0 O 1.3.3.3 [110/101] via 10.1.1.1, 00:00:01, FastEthernet0/0 O 1.2.2.2 [110/101] via 10.1.1.1, 00:00:01, FastEthernet0/0 192.168.13.0/30 is subnetted, 1 subnets O 192.168.13.0 [110/74] via 10.1.1.1, 00:05:11, FastEthernet0/0 33.0.0.0/32 is subnetted, 1 subnets O 33.33.33.33 [110/75] via 10.1.1.1, 00:05:11, FastEthernet0/0 3.0.0.0/32 is subnetted, 1 subnets O 3.3.3.3 [110/75] via 10.1.1.1, 00:05:11, FastEthernet0/0 111.0.0.0/32 is subnetted, 1 subnets O 111.111.111.111 [110/11] via 10.1.1.1, 00:05:11, FastEthernet0/0 10.0.0.0/24 is subnetted, 3 subnets O 10.4.4.0 [110/74] via 10.1.1.1, 00:05:11, FastEthernet0/0 11.0.0.0/32 is subnetted, 1 subnets O 11.11.11.11 [110/11] via 10.1.1.1, 00:05:11, FastEthernet0/0 133.133.0.0/32 is subnetted, 1 subnets O 133.133.133.133 [110/75] via 10.1.1.1, 00:05:11, FastEthernet0/0