How to do Ips range doesn't communicate with another range

[jopeme]

Hello.
I have a network with 172.30.0.0/255.255.255.0 range. For example small workgroups do ranging from 172.30.0.1 to 172.30.0.25, then another working group ranging from 172.30.0. 26 to 172.30.0.50.

As I can do to make the first range ips are doesn't see to the second rank? I image i can use firewall but i have no idea how to.
Thanks.

[christian]

Not so easy, first because you need to clarify a bit: what do you mean when you say "doesn't see"?
Are these devices on same physical segment (same LAN)? Then FW would never be in the middle to control who/what is seeing what 
Aside netmask that may help a little providing some kind of segregation, better approach would be VLAN. But again, we are discussing about network stuff which is perhaps not what you do need even if you express it in term of network first.