How IPv4 Network Assignments Work
There are 4,294,967,296 available IPs within the IPv4 address space.
These addresses are controlled by the Internet Assigned Numbers Authority, better known as IANA.
The Internet Assigned Numbers Authority (IANA) is responsible for the global coordination of the DNS Root, IP addressing, and other Internet protocol resources. http://www.iana.org/
The Internet Assigned Numbers Authority (IANA) is a department of ICANN responsible for coordinating some of the key elements that keep the Internet running smoothly. While the Internet is renowned for being a worldwide network free from central coordination, there is a technical need for some key parts of the Internet to be globally coordinated ? and this coordination role is undertaken by IANA.
Specifically, IANA allocates and maintains unique codes and numbering systems that are used in the technical standards (?protocols?) that drive the Internet. http://www.iana.org/about/
You can think of IANA/ICANN as the mother ship of IP addressing, and the network blocks they control as smaller ships or pods, which they can allocate to any of the five Regional Internet Registries: ARIN, RIPENCC, APNIC, LACNIC and AFRINIC.
- 0.0.0.0/8 ("This" Network) http://tools.ietf.org/html/rfc1122#section-22.214.171.124
- 10.0.0.0/8 (Private-Use Networks) http://tools.ietf.org/html/rfc1918
- 169.254.0.0/16 ?(link? local block) http://tools.ietf.org/html/rfc3927
- 172.16.0.0/12 (Private-Use Networks) http://tools.ietf.org/html/rfc1918
- 192.0.0.0/24 (IETF protocol assignments) http://tools.ietf.org/html/rfc5736
- 192.0.2.0/24 (This block is assigned as "TEST-NET-1" for use in ?documentation and example code.? It is often used in conjunction with ?domain names example.com or example.net in vendor and protocol ???documentation) http://tools.ietf.org/html/rfc5737? AND http://tools.ietf.org/html/rfc1166
- 192.168.0.0/16 (Private-Use Networks) http://tools.ietf.org/html/rfc1918
- 198.18.0.0/15 (benchmark ?tests of network interconnect devices) http://tools.ietf.org/html/rfc2544
- 198.51.100.0/24 (This block is assigned as "TEST-NET-2" for use in ?documentation and example code.? It is often used in conjunction with ?domain names example.com or example.net in vendor and protocol ???documentation) http://tools.ietf.org/html/rfc5737
- 203.0.113.0/24 (This block is assigned as "TEST-NET3" for use in ?documentation and example code.? It is often used in conjunction with ?domain names example.com or example.net in vendor and protocol ???documentation) http://tools.ietf.org/html/rfc5737
- 126.96.36.199/4 (IPv4 multicast address assignments) http://tools.ietf.org/html/rfc3171
- 240.0.0.0/4 (reserved for future use) http://tools.ietf.org/html/rfc1112#section-4
The above consists of 588,514,304 IPv4 addresses that should never be allowed entrance to your network. The addresses above are known as Bogons or Partial Bogons. In addition to these addresses there is another group of Bogons we need to consider: Full Bogons.
Full Bogons include IP addresses allocated to the Regional Internet Registries, but not yet assigned to an end-user, plus the Partial Bogons above. As of the date of this article the Full Bogon list includes 883,533,480 total addresses, consisting of the 588,514,304 addresses above and 295,019,176 unassigned addresses. Generally speaking, none of these addresses should be allowed entrance to your network.
The use of Bogon IPs is a favorite tactic of hackers, spammers and criminal cyber-gangs. Block these networks from your network.
The Full Bogon List is dynamic and changes daily. Country IP Blocks maintains a list of all these addresses in its databases and updates the data as it changes throughout the day.
IPv4 Address allocations are assigned by the five Regional Internet Registries (RIRs), with each registry typically, but not always, responsible for a certain area of the globe:
ARIN: North America
RIPENCC: Europe, Russia
APNIC: Asia Pacific
LACNIC: Latin America and the Caribbean
As IANA allocates resources to the Regional Internet Registries, each registry then assigns its IPv4 resources to ISPs and end-users. It is here these resources are divided into continents, countries and network ranges.
Each of the RIRs maintains a database of Whois information on all their assignees. This generally identifies the Network Range, CIDR (occasionally), Name, Organization, POC and country as well as other information such as abuse contacts, etc.
Unfortunately, this information is inconsistent. ARIN provides some of the best information, while many of the other RIRs provide information of lesser quality.
While many IPv4 address assignments are fairly static, others are not. IPv4 network assignments are created and deleted on a daily basis. Over the course of 2011 nearly 30% of all IPv4 networks changed hands. That is close to one billion. Some were reassigned, others become bogons.
Country IP Blocks maintains information on all 4,294,967,296 IPv4 addresses (and the IPv6 address space). We track and store changes to the IPv4 space and update the data daily.