Authentication Kerberos is a protocol that provides secure network authentication and support for single sign-on to network resources: see Using Kerberos. Because of limitations in the Windows OS, users that originally logged in using Kerberos authentication cannot reconnect automatically if their old session is no longer available. Therefore, while users logging in with cleartext or DHX-encrypted passwords silently reconnect after a cluster failover, clients logging in with Kerberos may be disconnected.