vRtrIsisLevelAuthKey is the authentication key string used to verify the authenticity of packets sent by neighboring routers on an IS-IS interface at this level. For authentication to succeed both the authentication key and the authentication type defined by the vRtrIsisLevelAuthType variable must match. If vRtrIsisLevelAuthType is set to 'password', vRtrIsisLevelAuthKey can include any ASCII character. Authentication can be configured globally and applied to all ISIS levels or it can be configured on a per level basis. The most specific value is used. If the value of vRtrIsisLevelAuthType is 'useGlobal', then the global values, if any, defined in vRtrIsisAuthKey and vRtrIsisAuthType are used instead. When read, vRtrIsisLevelAuthKey always returns an Octet String of length zero.