Private Subnets

There are three IP network addresses reserved for private networks. They can be used by anyone setting up internal IP networks, such as a lab or home LAN (Local Area Network) behind a NAT (Network Address Translation) or proxy server or a router. The most important use of this private subnet is for Virtual Local Area Network (VLAN). IT is always safe to use these because routers on the Internet will never forward packets coming from these addresses. The Internet Assigned Numbers Authority (IANA) has reserved the following three blocks of the IP address space for private internets:

 
IP Address range                          Slash notation                    Address class       
10.0.0.0 – 10.255.255.255            (10.0.0.0/8 prefix)                Class A       
172.16.0.0 – 172.31.255.255        (172.16.0.0/12 prefix)          Class B       
192.168.0.0 -192.168.255.255      (192.168.0.0/16 prefix)        Class C