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.To configure the maximum reservable bandwidth as an absolute value for MPLS LSPs on the interface, enter the following commands as displayed in the following example.
device# configure device(config)# router mpls device(config-router-mpls)# mpls-interface ethernet 0/1 device(config-router-mnpls-if-eth-0/1)# rsvp device(config-roouter-mpls-if-eth-0/1-rsvp)# reservable-bandwidth 10000
To configure the maximum reservable bandwidth as a percentage of the total interface bandwidth for MPLS LSPs on the interface, enter the following commands as displayed in the following example.
device# configure device(config)# router mpls device(config-router-mpls)# mpls-interface ethernet 0/1 device(config-router-mpls-if-eth-0/1)# rsvp device(config-router-mpls-if-eth-0/1-rsvp)# reservable-bandwidth percentage 80
When maximum reservable bandwidth is changed from an absolute value to a percentage value, and vice versa, the following advisory message is displayed on the console to indicate this configuration change.
device# configure device(config)# router mpls device(config-router-mpls)# mpls-interface ethernet 0/1 device(config-router-mpls-if-eth-0/1)# rvsp device(config-router-mpls-if-eth-0/1-rsvp)# reservable-bandwidth percentage 40 Maximum reservable bandwidth is changed from 30 kbps to 40%
Note
When the maximum reservable bandwidth is configured as either an absolute value, or a percentage value, the value is recalculated and updated to the latest value.To set the maximum reservable bandwidth back to the default value (the total physical bandwidth of the interface) when the absolute value or percentage value is used, enter the no form of the command as displayed in the following example.
device# configure device(config)# router mpls device(config-router-mpls)# mpls-interface ethernet 0/1 device(config-router-mpls-if-eth-0/1)# rsvp device(config-router-mpls-if-eth-0/1-rsvp)# no reservable-bandwidth percentage 80
By default, the reservable bandwidth is the same as the maximum available bandwidth on the interface. When the amount of reservable bandwidth is greater than the maximum available bandwidth, then the link can be oversubscribed. When the reservable bandwidth is less than the maximum available bandwidth, then LSPs cannot reserve all physical bandwidth on the interface. When the reservable-bandwidth command is applied to the primary port within a LAG, the bandwidth configured for that port applies to the entire LAG, regardless of any change to the number of active ports within the LAG.
Changing the amount of reservable bandwidth on an interface causes the amount of unreserved bandwidth to be recalculated. In addition, it may cause an IS-IS TE LSP to be issued, as well as possibly pre-empt existing LSPs when bandwidth reservations can no longer accommodate them.
The output from the show running-config router mpls command and the show router mpls interface [ ethernet slot/port ] command displays the maximum reservable bandwidth configuration. Depending on the interface configuration, the show commands displays the maximum reservable bandwidth as an absolute value, or as a percentage value. When the no form of the reservable-bandwidth command is used, the default value of the interface bandwidth is also displayed in both show command outputs.