IS-IS can be configured to use an incremental shortcut LSP SPF optimization algorithm. Incremental shortcut LSP SPF optimization is more efficient when updating the routes in cases where the shortcut LSP state change does not influence the topology. Incremental Shortcut LSP SPF Optimizations are enabled by default.
Note
If you disable the partial SPF optimizations, IS-IS automatically disables the incremental SPF optimizations and always runs full SPF. However, the reverse is not true: disabling incremental SPF optimizations does not disable partial optimizations.Note
Incremental Shortcut SPF optimizations are not applicable to LSP shortcuts with metrics configured on them.Note
Incremental Shortcut SPF optimizations are not applicable to LSP shortcuts with negative relative metrics configured.Note
Incremental Shortcut SPF optimizations are not applicable to announced LSP shortcuts.