I believe that if both devices you want no to speak with each other are on 2960 the "switchport protected" should work.
But you can configure with private vlan.
let's say client A is in port f0/1 and client B in port f0/2
Parent (main) VLAN is 100 and child is 999
You would configure the VLANs in ALL switches.
vlan 999
private-vlan isolated
vlan 100
private-vlan primary
private-vlan association 999
Now you would need to configure the ports.
int range f0/1 - 2
switchport mode private-vlan host
switchport private-vlan host-association 100 999
If the interfaces will talk to other VLANs, you need to configure the SVI to understand it will serve the private VLANs.
interface vlan 100
private-vlan mapping 999
That's it, but notice that now interface f0/1 will not talk to f0/2 and to any other interface inside vlan 100, if you want a port to communicate to f0/1 or f0/2 this new port would need to be configured as a promiscuous one (In case it needs to talk to both of them) or create a community private-vlan and configure the ports desired on it. (F0/1 and F0/2 can't be on the same community VLAN or they'll be able to talk to each other).
If the intention is to prevent one specific port from talking to all the others, you can put only this interface in the private VLAN instead of both.
wrote too much, if this answers your question let me know, or we can create a practical scenario for it.
