Fault tolerance is the ability of a system to continue functioning in the event of a failure of one or more of its components. Fault tolerance can ensure a secondary network path is available if the primary connection fails.
Fault tolerance can be achieved by using redundant components, such as network cards, cables, switches, routers, etc., that can take over the function of the failed component without interrupting the service.
References: https://www.comptia.org/training/resources/exam-objectives/comptia-server-sk0-005-exam- objectives (Objective 2.2)