Isolate LANs

Hello again

So this is a rather simple question I reckon but I need to be pointed in the right direction.

I have two LANs on two different interfaces. and Hosts on the first network can reach hosts on the second network. This is expected and working as it should. However if I want to isolate the LANs from being able to talk to each other, how would I go about doing that? Is it by using VLANs or are there other ways to achieve this (like ACL)? I should also mention that the LANs need to be able to access the Internet which is on a third interface on the gateway and available through NAT.

Thanks in advance!

this is typically the role of the firewall feature (ACL if you want, but this is more Cisco terminology).

Have a look at the doc :

Thanks, will read up on that later today!