Cisco Wireless :: How To Block P2P Traffic Of Clients Connected To Same SSID On WLC 4400

I use two wlc 4400 (4.2.x version) with a mobility domain and one ssid, both wlc are connected to a cisco l2 switch infrastructure. On the wlc I use the p2p blocking action 'drop' [URL] to isolate the clients from each other. Does only unicast traffic is blocked or also multicast and broadcast traffic like arp requests?Concerning blocking p2p traffic of clients connected to the same ssid but different controllers I found the following statement in the LAP FAQs [URL]

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 the default setting), 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.
 
what's the best practise to prevent this inter wlc client traffic? I already read about using acls on the wlc dynamic interfaces, or private vlans on the l2 switch vlans where the dynamic interfaces are connected to. Is it allowed to completely isolate the wlc from each other on these dynamic interfaces with acls or private vlans or do the wlc need to see each other on this interfaces (e.g. heart beat)?