In addition to the Make-Before-Break (MBB) support when the PCC receives a path update, as described in Behavior of the LSP path update, an RSVP-TE LSP supports the MBB procedure for any parameter configuration change, including the PCEP-related commands when they result in a change to the path of the LSP.
If the user adds or modifies the path-profile command for an RSVP-TE LSP, a Config Change MBB is only performed if the path-computation-method pce, pce-report, or pce-control options are enabled on the LSP. Otherwise, no action occurs. When path-computation-method pce, pce-report, or pce-control are enabled on the LSP, the Path Update MBB (tools perform router mpls update-path) is failed, resulting in a no operation.
MBB is also supported for the Manual Resignal and Auto-Bandwidth MBB types.
When the LSP goes into a MBB state at the ingress LER, the behavior is dependent on the operating mode of the LSP.