The simplest case of a link is a start-to-start (SS) or finish-to-finish (FF) link between two activities that are already finish-to-start (FS) connected. The more complex case of a redundant link is an SS link, FF link, or no-lag FS link connecting an activity to a successor, which, topology constant, cannot acquire a zero gap under any combination of durations and lags, because the successor is inevitably driven by a successor to the activity. The reverse of a redundant link is a valid link.
Redundant links can be hidden, displayed, faded, or shown. You can also tell if a link is redundant by opening its object property window. In the bottom left, it will display if it’s redundant or valid.
NOTE: Redundancy options through the menu bar are continually checked; rather, these are one-time operations, which must be done periodically as the schedule evolves.