Authentication survivability is a feature that allows the device to remain operational when a remote link failure occurs between a Gateway cluster and a RADIUS server that is either in the cloud or a datacenter. Authentication survivability enables the Gateway cluster to cache successful authentication requests from the RADIUS server and use them to authenticate clients when the RADIUS server is unreachable. Authentication survivability also allows clients to use MAC caching or MAC authentication bypass (MAB) methods to access the network when the RADIUS server is down. Reference: https://www.arubanetworks.com/assets/tg/TG_AuthSurvivability.pdf