This indicates whether tunnel reversion -- automatically switching traffic back to this tunnel once it recovers after having failed over to a backup -- is turned on or off. An admin turns this off deliberately on tunnels where an unplanned second switch-back could itself cause a brief disruption, preferring to schedule the switch-back manually during a maintenance window instead. For example, a critical tunnel with reversion off that recovers from a fault will stay on its backup path indefinitely until an admin manually reverts it, rather than auto-switching back the moment the primary looks healthy.