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CCKM Client Disconnect Bugs in 7.0/7.2

There are several  bugs that can cause CCKM clients periodically to be disconnected in WLC 7.0/7.2.  This tip explains the bugs, and how different 7.0/7.2 builds are vulnerable to them.

CSCtt70290 - this bug causes a CCKM client to be disconnected if the session timeout occurs after the client has roamed.  Workaround: disable the session-timeout on the WLAN.  This bug affects 7.0.98.0 through 7.0.220.0 and 7.0.235.0. This was a day 1 behaviour when CCKM feature was introduced.

Unfortunately, the "fix" for the CSCtt70290 problem, which was committed in 7.0.230.0 and 7.2.103.0, caused:

CSCty07036 - this bug causes a CCKM client to be disconnected if the group key (broadcast key) rotation occurs after the client has roamed.  Partial workaround: increase the broadcast key rotation timer to its maximum (one day.)

Because  the group key rotation problem is considered to be more severe than the  session timeout, for the 7.0.235.0 "MR3.5" release, the CSCtt70290 bad codefix was backed out via CSCtz19309.  Consequently, the 7.0.235.0 behavior reverts to the pre-7.0.230.0 behavior, i.e. group key rotation works, but session timeout causes client disconnects.

The real fix for both of these problems is addressed via CSCty07036, which fix is in the 7.0.240.0 and 7.2.110.0 releases.

This table shows, for the various releases in 7.0/7.2, whether broadcast key rotation or session timeout is broken for CCKM clients:              

ReleaseGroup Key Rotation
Session Timeout
7.0.98.0 - 7.0.220.0, 7.1.91.0WorkingNot Working*
7.0.230.0Not WorkingWorking
7.0.235.0, 7.0.235.3 WorkingNot Working*
7.0.240.0WorkingWorking
7.2.103.0Not WorkingWorking
7.2.110.0, 7.3Working

Working

*For voice deployments it is recommended to disable Session Timeout to avoid disruption in service.

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