Layer 3 Routing Commands 1645bandwidth is defined by the “bandwidth” command. Because the defaultreference bandwidth is 100 Mbps, OSPF uses the same default link cost for allinterfaces whose bandwidth is 100 Mbps or greater. To change the referencebandwidth, use the auto-cost command, specifying the reference bandwidthin megabits per second. The different reference bandwidth can beindependently configured for OSPFv2 and OSPFv3.Syntaxauto-cost reference-bandwidth ref_bw• ref_bw — The reference bandwidth in Mbps (Range: 1–4294967).Default ConfigurationThe default reference bandwidth is 100 Mbps.Command ModeOSPFv2 or OSPFv3 Router Configuration mode.User GuidelinesThere are no user guidelines for this command.ExampleThe following example configures a reference bandwidth of 500 Mbps.console(config-router)#auto-cost reference-bandwidth 500bandwidthBy default, OSPF computes the link cost of an interface as the ratio of thereference bandwidth to the interface bandwidth. Reference bandwidth isspecified with the auto-cost command. For the purpose of the OSPF link costcalculation, the bandwidth command specifies the interface bandwidth. Thebandwidth is specified in kilobits per second. If no bandwidth is configured,the bandwidth defaults to the actual interface bandwidth for port-basedrouting interfaces and to 10 Mbps for VLAN routing interfaces. Thiscommand does not affect the actual speed of an interface.
