Brocade FastIron Ethernet Switch Layer 3 Routing Configuration Guide - Manual (Page 270)

• LAG group - The combined bandwidth of all the ports.
• Virtual interface - The combined bandwidth of all the ports in the port-based VLAN that contains the
virtual interface.
The default reference bandwidth is 100 Mbps. You can change the reference bandwidth to a value
from 1 - 4294967.
If a change to the reference bandwidth results in a cost change to an interface, the device sends a
link-state update to update the costs of interfaces advertised by the device.
NOTE
If you specify the cost for an individual interface, the cost you specify overrides the cost calculated by
the software.
Interface types to which the reference bandwidth does not apply
Some interface types are not affected by the reference bandwidth and always have the same cost
regardless of the reference bandwidth in use:
• The cost of a loopback interface is always 1.
• The cost of a virtual link is calculated using the Shortest Path First (SPF) algorithm and is not
affected by the auto-cost feature.
• The bandwidth for tunnel interfaces is 9 Kbps and is also subject to the auto-cost reference
bandwidth setting.
Changing the reference bandwidth
To change the reference bandwidth, enter a command such as the following at the OSPF
configuration level of the CLI.
device(config)# router ospf
device(config-ospf-router)# auto-cost reference-bandwidth 500
The reference bandwidth specified in this example results in the following costs:
• 10 Mbps port’s cost = 500/10 = 50
• 100 Mbps port’s cost = 500/100 = 5
• 1000 Mbps port’s cost = 500/1000 = 0.5, which is rounded up to 1
The costs for 10 Mbps and 100 Mbps ports change as a result of the changed reference bandwidth.
Costs for higher-speed interfaces remain the same.
Syntax: [no] auto-cost { reference-bandwidth num | use-active-ports }
The num parameter specifies the reference bandwidth and can be a value from 1 - 4294967. The
default is 100.
To restore the reference bandwidth to its default value and thus restore the default costs of interfaces
to their default values, enter the following command.
device(config-ospf-router)# no auto-cost reference-bandwidth
Determining cost calculation for active ports only on LAG and VE interfaces
The default operation is for cost calculation of OSPF interfaces to be based upon all configured ports.
There is also an option for the auto-cost reference-bandwidth command for the calculation of OSPF
costs on active ports of LAG and VE interfaces. This option allows you to calculate cost based on the
Interface types to which the reference bandwidth does not apply
270 FastIron Ethernet Switch Layer 3 Routing Configuration Guide
53-1003087-04