What are the network ranges we can always use for our LANs?

In each network class there are private network range which you can use for your network. These networks are not routable to internet (you can NAT the private IP to public IP to use internet)

Class A:

private range: 10.0.0.0 to 10.255.255.255

Class B:

private range: 172.16.0.0 to 172.31.255.255

Class C:

private range: 192.168.0.0 to 192.168.255.255

Three ranges we can always use in our LANs:

1. Class A (10.0.0.0 - 10.255.255.255)

2. Class B (172.16.0.0 - 172.31.255.255)

3. Class C (192.168.0.0 - 192.168.255.255)

The most common network range used by /27 subnets for either class B or class C. This is used to accomodate 30 IPs which in many cases will suffice for a department