Client Reason Code…Description…Meaning
0…noReasonCode…Normal operation.
1…unspecifiedReason…Client associated but no longer authorized.
2…previousAuthNotValid…Client associated but not authorized.
3…deauthenticationLeaving…The access point went offline, deauthenticating the client.
4…disassociationDueToInactivity…Client session timeout exceeded.
5…disassociationAPBusy…The access point is busy, performing load balancing, for example.
6…class2FrameFromNonAuthStation…Client attempted to transfer data before it was authenticated.
7…class2FrameFromNonAssStation…Client attempted to transfer data before it was associated.
8…disassociationStaHasLeft…Operating System moved the client to another access point using non-aggressive load balancing.
9…staReqAssociationWithoutAuth…Client not authorized yet, still attempting to associate with an access point.
99…missingReasonCode…Client momentarily in an unknown state.
Just posting it here for future reference
[...] 10.04 (or 9.04, tried both) wouldn’t, with the Intel Iwlagn drivers reporting in syslog a deauth (reason=6), basically the card spoke too soon. I eventually found the [...]