The reservable-bandwidth command is configurable on an MPLS-enabled interface at any time. The configuration of the command takes effect immediately upon preemption of the LSP.
When LSP preemption occurs, when the reservable bandwidth required for a specific LSP is not supported on the interface, then the LSP immediately goes down. When this occurs, an IGP advertisement of this configuration change is triggered and flooded throughout all ports on the network because the maximum reservable bandwidth configured on the interface is different from the value that was previously configured.
Note
When the maximum reservable bandwidth is configured as a percentage value for LAGs and VE interfaces, and ports go down, or new ports are added to the interface, the reservable bandwidth is recalculated as a percentage of the newly available bandwidth for that interface.