Hi Eric,
Great question! Here is the related info, note the nice change in WLC Version 4.2.x.x;
Q. In autonomous APs, Public Secure Packet Forwarding (PSPF) is used to avoid client devices associated to this AP from inadvertently sharing files with other client devices on the wireless network. Is there any equivalent feature in Lightweight APs?
A. The feature or the mode that performs the similar function of PSPF in Lightweight architecture is called peer-to-peer blocking mode. Peer-to-peer blocking mode is actually available with the controllers that manage the LAP.
If this mode is disabled on the controller, which is by default, it allows the wireless clients to communicate with each other through the controller. If the mode is enabled, it blocks the communication between clients through the controller.
It only works among the APs that have joined to the same controller. When enabled, this mode does not block wireless clients terminated on one controller from the ability to get to wireless clients terminated on a different controller, even in the same mobility group.
http://www.cisco.com/en/US/products/hw/wireless/ps430/products_qanda_item09186a00806a4da3.shtml
Configuring Peer-to-Peer Blocking
In controller software releases prior to 4.2, peer-to-peer blocking is applied globally to all clients on all WLANs and causes traffic between two clients on the same VLAN to be transferred to the upstream VLAN rather than being bridged by the controller. This behavior usually results in traffic being dropped at the upstream switch because switches do not forward packets out the same port on which they are received.
In controller software release 4.2, peer-to-peer blocking is applied to individual WLANs, and each client inherits the peer-to-peer blocking setting of the WLAN to which it is associated.
http://www.cisco.com/en/US/docs/wireless/controller/4.2/configuration/guide/c42wlan.html#wp1084832
Hope this helps!
Rob
