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6.0 Summit Radio
6.1.6
PMK Caching
PMK caching is an alternative to CCKM supported with WPA2. The goal
of PMK caching is to speed up roaming between APs by accomplishing
802.1X reauthentications without communicating with the authentica-
tion server. When a client does an initial authentication to the WLAN
infrastructure, both sides derive the information needed for reauthentica-
tions.
If there are no controllers, then standard PMK caching is used, and reau-
thentication information is cached only on the initial AP. When the client
tries to reauthenticate to that AP, the client and the AP use the cached
information to do the four-way handshake to exchange keys. If there are
controllers, then opportunistic PMK caching is used, and reauthentica-
tion information is cached on the controllers. When the client tries to re-
authenticate, the client and the controller behind the AP use the cached
information to do the four-way handshake to exchange keys.
Use the PMK Caching global setting to configure the type of PMK cach-
ing supported by your infrastructure. If the Summit radio is configured
for one type of PMK caching and the infrastructure supports the other
type, then PMK caching will not work, and every roam will require a full
802.1X authentication that requires interaction with an authentication
server.
If the active profile has an Encryption setting of WPA2 CCKM, then the
Summit radio ignores the PMK Caching global setting and attempts to
use CCKM.