Public Ip addresses must be unique across the entire Internet. Internet Assigned Numbers Authority (IANA) is the organization manages the supply of IP addresses to ensure that every publicly used IP addresses are unique. IANA has three branches:
- Asia Pacific Network Information Center (APNIC)
- American Registry for Internet Numbers (ARIN)
- Reseaux IP Europens Network Coordination Center (RIPE NCC)
These branches assign block of addresses to regional Internet Service providers (ISP), which in turn assign addresses to individuals and cooperations.
As more and more hosts are connected to the internet, the available IP addresses will run out sooner or later. To address the issue of not enough available public IP addresses, private IP addresses are developed. An IP address is considered private if the IP number falls within one of the three IP address ranges reserved for private uses by IETF (1 Class A network, 16 Class B networks, and 256 Class C networks):
Class A: 10.0.0.0 – 10.255.255.255
Class B: 172.16.0.0 – 172.31.255.255
Class C: 192.168.0.0 – 192.168.255.255
Private address space are officially defined in RFC 1918, you can read through the documentation.
If you have a private address and you want to connect to the Internet, you then need to translate the private addresses to public addresses. This translation process is called Network Address Translation (NAT). We will talk about NAT later.
ICND1 and ICND2 break down