M and MSM Series

MSM720 and Fast Roaming

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MSM720 and Fast Roaming

I am trying to enable fast roaming on a VSC for wireless voip phones with WPA2 preshared key. I have seen things online indicating it should be possible, but the MSM720 only enables 802.1x if WPA is dynamic. Is it possible?


MSM720xx config pdf that says.


Wireless protection be WPA or 802.1x (or being the operative word)
and a test prep sample question:

Question :
A network administrator is configuring a VSC that enforces WPA2 with preshared keys (PSK) on an HP Controller. The VSC must support Voice over IP (VoIP) applications, so the network administrator enables opportunistic key caching to support fast roaming. When the network administrator saves the VSC settings, an error indicates 802.1X is required. How should the network administrator resolve this error?

  1. By purchasing a premium mobility license for the controller, which will allow the controller to
    support opportunistic key cashing with 802.1X.
  2. By enabling 802.1X but leaving in WPA2 key source set to static so that both forms of authentication are supported.
  3. By enabling wireless mobility as an authentication method for meeting the fast roaming requirements.
  4. By enabling opportunistic key caching: this feature is not required for fast roaming in a VSC such as this.

Answer : B


I cannot figure out the solution offereed in the tes prep question.

New Member

Re: MSM720 and Fast Roaming

hi , 


As per my understanding from this document, the answer should be A. 




Fast roaming Although WPA with 802.1X strengthens security for wireless

communications, it has one drawback: it increases the time required to roam from one AP to
another because the station must reauthenticate with the new AP and agree on encryptionkeys. In
fact, 802.1X re-authentication is the most time-intensive part of the roamingprocess.To reduce this
latency, an MSM Mobility or Premium Mobility Controller applies opportunistic key caching.


Opportunistic key caching provides the following benefits to clients that support it:
delays associated with reauthentication Provides
hand-offs in less than 50 ms, as
required for time-sensitive services suchas voice Preserves
a user‘s RADIUS-assigned parameters
such as security, QoS, and VLAN, enabling a smooth transition of all services to which the user
has access Note that VSCs that do not implement 802.1X authentication neither
support—nor require—opportunistic key caching for achieving roams under 50 ms. For example,in
a VSC with no authentication and encryption, the client simply needs to associateto the new AP.
For a VSC that enforces WPA/WPA2-PSK, all APs and clients alreadyknow the PMK.