Dell EMC SmartFabric OS10 User Guide Release 10.5.0

Dynamic path cost calculation

Path cost of an interface (physical or port-channel) is calculated based on the speed of the port or port-channel. When the speed of the port or port-channel changes, the past cost recalculation is triggered based on the user defined configuration.

You can enable/disable dynamic recalculation of path cost using the spanning-tree path-cost command.

This cmd allows the protocol to do dynamic cost calculation whenever the channel-members are added or deleted. By default, this dynamic path cost calculation is enabled.

When dynamic path cost is disabled , protocol calculate the path cost when the port channel is coming up for the first time after creation or whenever dynamic path cost calculation is enabled and then disabled by management or when the user adds/removes member port to/from the port channel.

This feature allows the user to disable path cost re-calculation on link flap events. If disabled, the path cost of the lag is calculated based on the below formula LAG speed = speed of a single member * number of configured member ports (irrespective of its oper status).

Path cost changes only for the user event [addition/removal of channel-member]. Path cost is calculated based on the number of configured ports.

Dynamic path cost disable functionality is supported for VLT port channel.