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IPv4 and IPv6 Address Lengths

IPv4 addresses consist of 4 bytes (32 bits), while IPv6 addresses have 16 bytes (128 bits) in length. These bytes, referred to as octets, are commonly represented in dotted decimal notation for readability, separating each octet with a decimal point. This notation is more user-friendly and is the standard representation used by Internet Service Providers (ISPs).

Binary to Dotted Decimal Translation

In binary notation, an IPv4 address such as “11000000.10101000.00000001.00000000” translates to dotted decimal as “” Understanding the conversion between dotted decimal and binary is crucial in comprehending IPs and Subnets.

Internet Protocol (IP) Address Overview

The Internet Protocol (IP) is a communication protocol employed by networks to enable device communication. IP addresses, unique 8-bit numbers assigned to devices, function as virtual home addresses for internet-capable devices. There are two IP addressing standards: IPv4, the widely used standard, and IPv6, positioned to replace IPv4 due to the exhaustion of its address space.

Subnetting and IPv4 Origins

During the early days of the Internet, the US Department of Defense developed IPv4 in a quad dotted decimal format. As IPv4 addresses faced depletion in the late 1980s, IPv6 was introduced with eight subnets separated by colons. IPv4’s subnets, divided into five classes (A, B, C, D, E), have distinct purposes ranging from large companies to multicast addressing and scientific studies.

IPv4 Address Classes

IPv4 addresses are classified into five classes, each serving specific purposes:

  • Class A:
  • Starting Address:
  • Ending Address:
  • Purpose: Designed for use in very large companies like Google.
  • Class B:
  • Starting Address:
  • Purpose: Designed for use in medium-sized companies.
  • Ending Address:
  • Class C:
  • Starting Address:
  • Ending Address:
  • Purpose: Designed for use in small-sized companies.
  • Class D:
  • Starting Address:
  • Ending Address:
  • Purpose: Not used in the public sector; reserved for multicast addressing.
  • Class E:
  • Starting Address:
  • Ending Address:
  • Purpose: Not used in the public sector; reserved for scientific studies.

Class A IP Addresses Network Bits Subnet Mask Number of Subnets Number of Hosts

Network BitsSubnet MaskNumber of SubnetsNumber of Hosts
/9255.128.0.02 (0)8388606
/10255.192.0.04 (2)4194302
/11255.224.0.08 (6)2097150
/12255.240.0.016 (14)1048574
/13255.248.0.032 (30)524286
/14255.252.0.064 (62)262142
/15255.254.0.0128 (126)131070
/16255.255.0.0256 (254)65534
/17255.255.128.0512 (510)32766
/18255.255.192.01024 (1022)16382
/19255.255.224.02048 (2046)8190
/20255.255.240.04096 (4094)4094
/21255.255.248.08192 (8190)2046
/22255.255.252.016384 (16382)1022
/23255.255.254.032768 (32766)510
/24255.255.255.065536 (65534)254
/25255.255.255.128131072 (131070)126
/26255.255.255.192262144 (262142)62
/27255.255.255.224524288 (524286)30
/28255.255.255.2401048576 (1048574)14
/29255.255.255.2482097152 (2097150)6
/30255.255.255.2524194304 (4194302)2

Class B IP Addresses Network Bits Subnet Mask Number of Subnets Number of Hosts

Network BitsSubnet MaskNumber of SubnetsNumber of Hosts
/17255.255.128.02 (0)32766
/18255.255.192.04 (2)16382
/19255.255.224.08 (6)8190
/20255.255.240.016 (14)4094
/21255.255.248.032 (30)2046
/22255.255.252.064 (62)1022
/23255.255.254.0128 (126)510
/24255.255.255.0256 (254)254
/25255.255.255.128512 (510)126
/26255.255.255.1921024 (1022)62
/27255.255.255.2242048 (2046)30
/28255.255.255.2404096 (4094)14
/29255.255.255.2488192 (8190)6
/30255.255.255.25216384 (16382)2

Supernetting (CIDR) Chart CIDR – Classless Inter-Domain Routing. 

Note: The Number of Class C networks must be contiguous. For example, represents the following block of addresses:,, and 

CIDR BlockSupernet MaskNumber of Class C AddressesNumber of Hosts

IP Address Classes and Ranges

ARIN oversees IP address classes, including Class A, B, and C, each designated for specific purposes. Additionally, ARIN manages reserved address ranges, such as those for private (non-routed) use and other reserved addresses like loopback and multicast.

IP Address Allocation and Supernetting

To cater to the evolving internet landscape, ARIN facilitates the allocation of IP addresses by employing CIDR (Classless Inter-Domain Routing). This enables the aggregation of Class C networks into supernet blocks, improving address space utilization and management.

Contact ARIN for IP Address Inquiries

For organizations in need of IP addresses, ARIN serves as a crucial resource. Those seeking IPv4 connectivity are encouraged to reach out to ARIN for information on the acquisition process.

Decoding IPv4 Subnet Masks

Understanding binary is key to unraveling the intricacies of IPv4 subnet masks. Let’s delve into the subnet masks presented at the beginning of this discussion: / and

The Essence of Subnet Masks

At its core, a subnet mask partitions an IP address into network and host portions. In simpler terms, it designates the street (network) and individual houses (hosts) on that street. Consider it as the blueprint that defines which part of the TCP/IP address denotes your network and what’s available for hosts.

Breaking Down

Take the subnet mask as an example. This implies that the first three octets of the address are allocated to the network, making our network number 192.168.1. The remaining octet is reserved for hosts. The presence of “0” in the subnet mask ( signals that the fourth octet is available for host addresses. Consequently, our network can accommodate up to 254 computers.

Binary Representation

In binary, where each section is termed an octet due to the eight bits it comprises, the subnet mask translates to 11111111.11111111.11111111.00000000. Counting the ones reveals a total of 24, indicating the number of bits dedicated to the network portion.

Subnet Mask Shorthand: /24

Now, observe the expressions and Both notations convey the same information. The “24” signifies the number of bits assigned to the network portion of the address. This shorthand becomes crucial when dividing networks into subnetworks.

The Significance in Network Division

Understanding the relationship between the address and subnet mask, especially through shorthand notations like “/24,” becomes pivotal when dividing a network into multiple subnetworks. This knowledge empowers network administrators to efficiently manage and allocate IP addresses across diverse segments.

The Role of AFRINIC in IP Address Management

Internet Protocol Development

In the nascent stages of the internet, the development of Internet Protocol version 4 (IPv4) served as a foundational framework for computer networking. With the continuous expansion of the internet, the imperative for effective IP address management became increasingly evident.

The Birth of IANA and AFRINIC

The Internet Assigned Numbers Authority (IANA), now overseen by the Internet Corporation for Assigned Names and Numbers (ICANN), was established to govern IPv4 IP address management. During the late 1980s and into the 2000s, multiple organizations were founded to address the escalating demand for IP addresses and the need for structured distribution.

The Foundation of AFRINIC

In 2004, the African Network Information Centre (AFRINIC) was established as a non-profit organization and designated as one of the five Regional Internet Registries (RIRs). AFRINIC operates within the regions covering Africa and the Indian Ocean islands, playing a pivotal role in the issuance of Internet number resources.

AFRINIC’s Functions and Authority

AFRINIC undertakes the crucial task of managing the allocation of IP addresses within its region. Beyond this, the organization actively engages in shaping consensus-based policies and driving Internet development through educational and outreach initiatives. With the authority to implement policies formed through transparent and continuous community input, AFRINIC holds a central role in defining the regulations governing Internet numbers in its designated regions.

The Role of ARIN in IP Address Management

Internet Protocol Development

In the early stages of the internet, developers crafted Internet Protocol version 4 (IPv4) as a systematic means for computer networking. As the internet expanded, the need for efficient IP address management became apparent.

The Birth of IANA and ARIN

The Internet Assigned Numbers Authority (IANA), now under the umbrella of the Internet Corporation for Assigned Names and Numbers (ICANN), emerged to oversee IPv4 IP address management. In the late 1980s and through the 2000s, several organizations were established to address the growing demand for IPs and the necessity for organized distribution.

The Foundation of ARIN

In 1997, the American Registry for Internet Numbers (ARIN) was established as a nonprofit organization and became one of the five Regional Internet Registries (RIRs). Operating in the regions that encompass parts of the Caribbean, Canada, and the United States, ARIN plays a pivotal role in issuing Internet number resources.

ARIN’s Functions and Authority

ARIN not only manages the allocation of IP addresses but also fosters consensus-based policies and promotes Internet advancement through education and outreach initiatives (ARIN, 2013). It operates with the authority to implement policies developed through open and ongoing community input, essentially dictating the rules surrounding Internet numbers.

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