This controls whether Level-1 Hello authentication is checked on received PDUs as well as applied to sent ones. Despite the SYNTAX using enable(1)/disable(2) as its actual labels, the source DESCRIPTION text describes them as "true(1)/false(2)" -- reading it against the real enum: enable(1) authenticates only outgoing Hello PDUs (incoming ones are accepted unchecked), while disable(2), the default, authenticates both directions. An admin would enable send-only during a password rollout to avoid dropping neighbors that haven't been updated yet.