Separate networks accessing one router with subnet mask

Hello All,

I am trying to setup multiple separate networks that all access the same Internet router. I don’t want the networks to be able to “see” each other, i.e; you can ping network A from network B. All networks need to be able to access the single Internet router.

In my lab I was toying with using subnet masks to accomplish this but I don’t think I am setting it up right. Here’s a sceanario;

Internet Router:
Internal Network 192.168.1.1
Subnet mask: 255.255.0.0

Network A machine 192.168.1.1 255.255.255.0
Network B machine 192.168.2.1 255.255.255.0

Both machines can ping the Ineternet router but they can also both ping each other. What configuration should I use so that they can’t?

TYIA,

Eric