This read-write TruthValue object controls whether an N_port's Fabric Login (FLOGI) is rejected on this VSAN when its Port World Wide Name is not already present in the VSAN's WWN database; by default (false) an unlisted port still gets static VSAN membership, but setting it true denies the login outright. A security-conscious administrator enables this to enforce strict port-level access control on a VSAN, preventing unauthorized or unrecognized devices from joining the fabric. For example, setting vsanDenyUnknownWwn to true on a VSAN carrying sensitive storage traffic blocks any new HBA whose WWN has not been explicitly added to that VSAN's WWN list.