- Now a days we are commonly using both IPv4 and IPv6 versions of IP addresses. This have finite pools of numbers.
- For IPv4, this pool is 32-bit (2^32) in size and contains 4,294,967,296 IPv4 addresses.
- For IPv6, this pool is 128-bit (2^128) in size and contains 340,282,366,920,938,463,463,374,607,431,768,211,456 IPv6 addresses.
- From this IPv4 and IPv6 addresses, some IP addresses are assigned to access the internet and some are used in private networks.
- This means the total number of IP address available for allocation in less than the total number in the pool.
- Every IP address is divided into two parts, one is networks and other is hosts.
- IP addresses are assigned to networks in different sizes is called "Blocks".
- The size of the block assigned is written after an oblique (/), which shows the number of IP addresses contained in that block.
- For example, if an Internet Service Provider(ISP) is assigned a IP as "10.10.16.10/16". Here it provides 32-16 = 16 which means the it has 2^16 (65,536) addresses in IPv4.
Purchase IP Blocks:
If you want to purchase IP Blocks then you need to contact one of the five "Regional Internet Registries" (RIRs).
- American Registry for Internet Numbers (ARIN).
- Latin America and Caribbean Network Information Center (LACNIC).
- RIPE Network Coordination Center (RIPE NCC).
- Africa Network Information Center (AFRINIC).
- Asia Pacific Network Information Center (APNIC).
The below image shows which RIR belongs to which region:
