How can I prevent clients from communicating on the LAN? Prevent users file and printer sharing settings from opening themselves up to other users who may be apt to peak into whats on the network.
On wired TCP/IP Ethernet networks clients on the same subnet directly talk to one another and don’t pass traffic through the router. Therefore the router cannot block traffic between clients given that the traffic doesn’t pass through it in the first place. You would have to implement this on switches that have such functionality. There are different approaches, such as ACLs or private VLANs.
In wireless networks with APs (not ad hoc) all traffic goes through the AP, so you can just turn off default forwarding to keep wireless clients from talking to one another. On Mikrotik APs you can also implement bridge firewalls to keep them from talking to wired clients you’re bridging radio interfaces into the wire, or implement the same security on the switch as above. Again, traffic doesn’t go through the router.
Also, this has absolutely nothing to do with NAT.