IP Address is also known as Internet Protocol Address. The Internet Protocol Address assignments are managed by the Internet Assigned Numbers Authority (IANA). IANA has divided the IP Addresses in two groups. First named as Public IP Address and second named as Private IP Address. The Public IP Address has to be unique in the whole world. Hence, Public IP Address is routable to internet. The Private IP Address is reserved to build private network controlled by the owner of the private network without coordination with IANA and the Private IP Address are not unique in the world. Hence, Private IP Address by default is not routable to internet. IANA has reserved the the following IP addresses to create Private Network by anyone:
  • Class A: 10.0.0.0 to 10.255.255.255
  • Class B: 172.16.0.0 to 172.31.255.255
  • Class C: 192.168.0.0 to 192.168.255.255

The table provides a quick guide for sizing Virtual Networks/SubNets. The Virtual Networks and SubNets are usually configured in Classless Inter Domain Routing (CIDR) notation (x.x.x.x/8, x.x.x.x/16, ... x.x.x.x/24). The largest possible Virtual Networks/SubNets is 10.x.x.x/8 and the smallest possible Virtual Networks/SubNets is 10.x.x.x/30. It is a leading practice to consider that we keep the minimum size of the Virtual Networks/SubNets at 3x plus level. While x is the size for the proposed Virtual Networks/SubNets Go-Live requirements. Virtual Networks and SubNets Size
Please note that hosting or Infrastructure as a Services(IaaS) provider may reserve additional IP Address in Virtual Networks/SubNets that one need to adjust and align for their Private Network Design.