IP address ranges are essential to the way devices communicate across networks, particularly over the internet. An IP address is a numerical label assigned to each device connected to a network that uses the Internet Protocol for communication. These addresses serve two primary functions: identifying the host or network interface and providing a location for routing traffic between devices. There are two versions of IP addresses in use today: IPv4 and IPv6, each with its distinct range of addresses. The related RFC is RFC 791, which defines the structure of IPv4 addresses and their range. https://en.wikipedia.org/wiki/IPv4 https://tools.ietf.org/html/rfc791

The IPv4 address range is defined by a 32-bit addressing system, allowing for approximately 4.3 billion unique addresses. These addresses are written in dotted decimal notation, divided into four octets. The total range of IPv4 addresses spans from 0.0.0.0 to 255.255.255.255. However, not all of these addresses are available for public use. Certain blocks of IPv4 addresses are reserved for specific purposes, such as private networks, multicast addresses, and loopback addresses. The related RFC is RFC 1918, which defines the private address ranges used within local networks. https://en.wikipedia.org/wiki/Private_IP_address https://tools.ietf.org/html/rfc1918

Within the IPv4 address range, private IP addresses are reserved for use in local networks. These private addresses cannot be routed on the public internet, which helps conserve the global pool of IPv4 addresses. The private address ranges defined by RFC 1918 are 10.0.0.0/8, 172.16.0.0/12, and 192.168.0.0/16. These ranges are commonly used in home and corporate networks where Network Address Translation (NAT) is employed to allow multiple devices to share a single public IP address when accessing the internet. The related RFC is RFC 3022, which explains how NAT works in conjunction with private IP addresses. https://en.wikipedia.org/wiki/Network_address_translation https://tools.ietf.org/html/rfc3022

IPv4 addresses also include specific ranges for special purposes. For example, the loopback range (127.0.0.0/8) is used by devices to send traffic to themselves for testing purposes, while the multicast range (224.0.0.0 to 239.255.255.255) is reserved for multicast communication, where one device sends traffic to multiple recipients. Additionally, addresses from 169.254.0.0/16 are used for Automatic Private IP Addressing (APIPA) in cases where a device cannot obtain an IP address through DHCP. The related RFC is RFC 5735, which defines special-use IPv4 address ranges. https://en.wikipedia.org/wiki/Reserved_IP_addresses https://tools.ietf.org/html/rfc5735

The exhaustion of IPv4 addresses led to the development and adoption of IPv6, which uses a 128-bit addressing system, providing a vastly larger address space. The total range of IPv6 addresses is approximately 340 undecillion, written in hexadecimal and separated by colons. Unlike IPv4, IPv6 was designed to provide enough address space to avoid the need for NAT and to support the growing number of devices connected to the internet. The related RFC is RFC 2460, which defines the IPv6 protocol and its address structure. https://en.wikipedia.org/wiki/IPv6 https://tools.ietf.org/html/rfc2460

Similar to IPv4, IPv6 also reserves certain address ranges for special purposes. For example, addresses starting with ::1/128 are reserved for loopback, and the Unique Local Address (ULA) range (fc00::/7) is reserved for local networks, similar to the private address ranges in IPv4. There are also link-local addresses, starting with fe80::/10, which are used for communication within a single network segment without requiring routing. The related RFC is RFC 4193, which defines ULA in IPv6 networks. https://en.wikipedia.org/wiki/Unique_local_address https://tools.ietf.org/html/rfc4193

Public IP addresses, whether in IPv4 or IPv6, are managed and allocated by Regional Internet Registries (RIRs) such as ARIN, RIPE NCC, and APNIC. These organizations distribute address blocks to Internet Service Providers and large organizations based on need and availability. Public IP address allocation follows strict guidelines to ensure efficient use of the available address space. The related RFC is RFC 2050, which outlines the policies for IP address allocation by RIRs. https://en.wikipedia.org/wiki/Regional_Internet_registry https://tools.ietf.org/html/rfc2050

In addition to public and private addresses, there are also reserved ranges for documentation and testing. For example, RFC 5737 defines specific IPv4 address blocks that should be used in documentation and examples to avoid conflicts with live network addresses. Similarly, IPv6 reserves addresses for testing and development environments, helping network engineers simulate and design network systems without interfering with actual internet traffic. The related RFC is RFC 5737, which defines address blocks reserved for documentation purposes. https://en.wikipedia.org/wiki/Reserved_IP_addresses https://tools.ietf.org/html/rfc5737

The transition from IPv4 to IPv6 has been a long process, as both protocols coexist on the internet. Many devices and networks still rely on IPv4, but the adoption of IPv6 is growing steadily. Dual-stack networks, where devices are assigned both IPv4 and IPv6 addresses, are commonly used to support the transition. This allows networks to remain compatible with older systems while taking advantage of the benefits of IPv6. The related RFC is RFC 4213, which outlines the mechanisms for IPv6 transition and coexistence with IPv4. https://en.wikipedia.org/wiki/IPv6_transition_mechanisms https://tools.ietf.org/html/rfc4213

The title of this RFC is “IP Address Ranges.” IP address ranges play a crucial role in network communication, providing a structured way to assign addresses to devices and route traffic across networks. With the limited space of IPv4 and the introduction of IPv6, the internet has evolved to accommodate the growing number of connected devices. Through reserved address ranges, special-use addresses, and private address blocks, the allocation and management of IP addresses remain essential to the functionality of the modern internet. The adoption of IPv6 ensures that the world will have sufficient address space for the foreseeable future, while the legacy of IPv4 continues to influence network design and operation.