Partial SPF optimizations

IS-IS employs certain partial SPF optimizations to make partial changes to the routing table in network change situations where the topology of the network has not changed but where there may be changes in the IP networks advertised.

These optimizations are termed partial SPF optimizations. IS-IS can be configured to perform a full SPF calculation when any network (non-topology) change occurs so that IS-IS always runs full SPF for all such network changes.

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.