Why is JBoss Negotiation logging a "Client not found in Kerberos database" error?

Issue

• Why is JBoss Negotiation logging a "Client not found in Kerberos database" error?

11:22:16,767 INFO  [STDOUT] principal's key obtained from the keytab
11:22:16,767 INFO  [STDOUT] Acquire TGT using AS Exchange
11:22:16,818 INFO  [STDOUT]             [Krb5LoginModule] authentication failed 
Client not found in Kerberos database (6) - CLIENT_NOT_FOUND
11:22:16,819 ERROR [SecurityDomainTestServlet] testDomain Failed
javax.security.auth.login.LoginException: Client not found in Kerberos database (6) - CLIENT_NOT_FOUND
        at com.sun.security.auth.module.Krb5LoginModule.attemptAuthentication(Krb5LoginModule.java:696)
        at com.sun.security.auth.module.Krb5LoginModule.login(Krb5LoginModule.java:542)
        at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
        at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
        at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
        at java.lang.reflect.Method.invoke(Method.java:597)
        at javax.security.auth.login.LoginContext.invoke(LoginContext.java:769)
        at javax.security.auth.login.LoginContext.access$000(LoginContext.java:186)
        at javax.security.auth.login.LoginContext$4.run(LoginContext.java:683)
        at java.security.AccessController.doPrivileged(Native Method)
        at javax.security.auth.login.LoginContext.invokePriv(LoginContext.java:680)
        at javax.security.auth.login.LoginContext.login(LoginContext.java:579)
        at org.jboss.security.negotiation.toolkit.SecurityDomainTestServlet.testDomain(SecurityDomainTestServlet.java:108)
        at org.jboss.security.negotiation.toolkit.SecurityDomainTestServlet.doGet(SecurityDomainTestServlet.java:77)
        at javax.servlet.http.HttpServlet.service(HttpServlet.java:617)
        at javax.servlet.http.HttpServlet.service(HttpServlet.java:717)
        at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:290)
        at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
        at org.jboss.web.tomcat.filters.ReplyHeaderFilter.doFilter(ReplyHeaderFilter.java:96)
        at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:235)
        at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
        at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:235)
        at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:191)
        at org.jboss.web.tomcat.security.SecurityAssociationValve.invoke(SecurityAssociationValve.java:183)
        at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:433)
        at org.jboss.web.tomcat.security.JaccContextValve.invoke(JaccContextValve.java:95)
        at org.jboss.web.tomcat.security.SecurityContextEstablishmentValve.process(SecurityContextEstablishmentValve.java:126)
        at org.jboss.web.tomcat.security.SecurityContextEstablishmentValve.invoke(SecurityContextEstablishmentValve.java:70)
        at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:127)
        at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:102)
        at org.jboss.web.tomcat.service.jca.CachedConnectionValve.invoke(CachedConnectionValve.java:158)
        at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:109)
        at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:330)
        at org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:829)
        at org.apache.coyote.http11.Http11Protocol$Http11ConnectionHandler.process(Http11Protocol.java:598)
        at org.apache.tomcat.util.net.JIoEndpoint$Worker.run(JIoEndpoint.java:451)
        at java.lang.Thread.run(Thread.java:619)
Caused by: KrbException: Client not found in Kerberos database (6) - CLIENT_NOT_FOUND
        at sun.security.krb5.KrbAsRep.<init>(KrbAsRep.java:72)
        at sun.security.krb5.KrbAsReq.getReply(KrbAsReq.java:448)
        at sun.security.krb5.Credentials.sendASRequest(Credentials.java:401)
        at sun.security.krb5.Credentials.acquireTGT(Credentials.java:350)
        at com.sun.security.auth.module.Krb5LoginModule.attemptAuthentication(Krb5LoginModule.java:672)
        ... 36 more
Caused by: KrbException: Identifier doesn't match expected value (906)
        at sun.security.krb5.internal.KDCRep.init(KDCRep.java:133)
        at sun.security.krb5.internal.ASRep.init(ASRep.java:58)
        at sun.security.krb5.internal.ASRep.<init>(ASRep.java:53)
        at sun.security.krb5.KrbAsRep.<init>(KrbAsRep.java:50)
        ... 40 more