Global IP Address Management: RIRs and LIRs Explained

The internet’s foundational architecture relies heavily on a robust, globally coordinated system for managing IP addresses. Without a structured approach to allocating and assigning these unique identifiers, the interconnectedness we take for granted would quickly devolve into chaos. For network engineers, system architects, and technical leads, a deep understanding of this system—particularly the roles of Regional Internet Registries (RIRs) and Local Internet Registries (LIRs)—is paramount. This article will demystify RIRs and LIRs, exploring their functions, the hierarchical model of IP address delegation, and their critical impact on network design, routing, and the future of the internet.

The Global IP Addressing Hierarchy

At the very top of the IP address management hierarchy sits the Internet Assigned Numbers Authority (IANA), a department of the Internet Corporation for Assigned Names and Numbers (ICANN). IANA is responsible for the global coordination of the Internet’s root DNS, IP addressing, and other internet protocol resources. It delegates large blocks of IP addresses to the five Regional Internet Registries (RIRs).

This delegation model ensures that IP address space is managed in a distributed yet coordinated manner, reflecting regional needs and policies. The RIRs, in turn, allocate smaller blocks of IP addresses to their members, which are primarily Local Internet Registries (LIRs). LIRs then assign these addresses to their end-users or for their own internal network infrastructure. This structured, top-down approach is fundamental to maintaining a stable and routable global internet.

Network cables in a data center — Rows of network equipment and cabling in a modern data center.

Regional Internet Registries (RIRs): Custodians of Regional IP Space

Regional Internet Registries (RIRs) are non-profit organizations responsible for managing and distributing IP address space and ASN (Autonomous System Number) resources within specific geographic regions. They operate under policies developed by their members, ensuring a transparent and community-driven approach to resource management.

There are five RIRs globally, each serving a distinct region:

AFRINIC: Africa
APNIC: Asia Pacific
ARIN: Canada, United States, and many Caribbean islands
LACNIC: Latin America and the Caribbean
RIPE NCC: Europe, the Middle East, and parts of Central Asia

The core functions of an RIR include:

Policy Development: Facilitating an open, bottom-up policy development process where members propose and refine policies governing resource allocation and assignment.
Resource Allocation: Allocating large blocks of IP addresses (both IPv4 and IPv6) and ASNs to LIRs within their service region based on established policies.
Database Maintenance: Operating and maintaining publicly accessible databases, such as WHOIS, which contain information about IP address allocations and assignments. This transparency is crucial for network troubleshooting and abuse reporting.
Reverse DNS Management: Managing the reverse DNS infrastructure for the IP address space they administer.
Training and Outreach: Providing educational resources and support to their members and the wider internet community.

Becoming a direct member of an RIR typically requires demonstrating a need for significant IP address space and adherence to regional policies. For instance, an organization might apply for provider-independent (PI) address space if it needs to multihome with multiple ISPs and maintain the same IP addresses regardless of which ISP it uses. This ensures routing stability and resilience, albeit potentially contributing to routing table growth^[1].

Local Internet Registries (LIRs): The Frontline of IP Distribution

Local Internet Registries (LIRs) are organizations that receive IP address space from an RIR and then assign it to their own customers or use it for their internal network infrastructure. Most LIRs are Internet Service Providers (ISPs), but large enterprises, academic institutions, and government entities with significant network operations can also qualify.

The primary responsibilities of an LIR include:

Obtaining Allocations: Applying to their respective RIR for IP address blocks (e.g., a /22 IPv4 block or a /32 IPv6 block) based on their demonstrated need and justification.
Assigning Addresses: Distributing smaller address ranges to their end-users (e.g., a /29 to a small business, a /48 to an enterprise for IPv6) or internal departments.
Managing Internal IP Space: Efficiently planning and managing their allocated IP space to ensure optimal utilization and prevent fragmentation.
Maintaining Assignment Records: Keeping accurate records of all assignments made to their customers, which are often submitted to the RIR’s WHOIS database.
Policy Contribution: Participating in the RIR’s policy development process, ensuring that allocation policies remain relevant and address the needs of the LIR community.

To become an LIR, an organization must typically meet certain criteria, such as having a clear network plan, demonstrating actual usage or a plan for significant usage of IP resources, and often having an existing or planned connection to the global internet via BGP. LIRs primarily receive provider-aggregatable (PA) address space, which means the IP blocks are part of a larger, aggregated block delegated to the LIR. This facilitates efficient routing by allowing ISPs to announce a single, larger route to their upstream providers, rather than numerous smaller routes^[2].

The Allocation and Assignment Process

The process by which IP addresses flow from IANA down to end-users involves distinct steps and terminology:

Global Delegation: IANA delegates large, unallocated IP blocks to RIRs.
RIR Allocation to LIRs: An LIR submits a request to its RIR, justifying the need for a specific block of IP addresses (e.g., IPv4 /22 or IPv6 /32). This justification often involves projections of customer growth or infrastructure expansion. The RIR reviews the request against its established policies. Upon approval, the RIR allocates the requested block to the LIR.
LIR Assignment to End-Users: The LIR then assigns smaller sub-blocks from its allocated space to its customers or uses them for its own network infrastructure. For example, an ISP (LIR) might assign a /29 IPv4 block to a business customer or a /56 IPv6 block to a residential subscriber.

A practical example of how this information is publicly available can be seen through a whois lookup:

whois 8.8.8.8

The output for Google’s public DNS server 8.8.8.8 would show details indicating it is assigned to Google LLC within the ARIN region, demonstrating how RIRs track and publish this crucial information.

Note: The minimum allocation size for IPv4 to an LIR is typically a /22 (1024 addresses) from ARIN/RIPE NCC, though exhaustion policies have made this increasingly rare. For IPv6, the standard allocation size to an LIR is a /32 (approximately 18 quintillion addresses), reflecting the vastness of the IPv6 address space. End-user assignments are much smaller, often a /48 or /56 for IPv6 to ensure ample subnetting capability for the end-site^[3].

IP addresses on a global network map — Abstract visualization of IP addresses connecting across a global network.

Key Distinctions and Operational Impact

Understanding the differences between RIRs and LIRs is crucial for effective network management and planning.

Feature	Regional Internet Registry (RIR)	Local Internet Registry (LIR)
Scope	Regional (e.g., Europe, North America)	Local/National (e.g., ISP, Enterprise network)
Primary Role	Policy development, allocation of large blocks to LIRs	Obtaining allocations from RIR, assigning to end-users
Membership Type	Non-profit, community-driven, often by LIRs and other entities	Typically ISPs, large enterprises, academic institutions
Resource Type	Receives large blocks from IANA, allocates to LIRs	Receives allocations from RIRs, assigns to end-users
Policy Influence	Sets regional policies through community consensus	Participates in RIR policy development, implements policies
Address Space	Manages broad IP address ranges	Manages specific allocated blocks, sub-assigns to customers

The distinction between provider-independent (PI) and provider-aggregatable (PA) address space is another critical concept.

Provider-Aggregatable (PA) Addresses: These are IP addresses assigned by an LIR (typically an ISP) from its own allocated block. If an organization using PA addresses changes ISPs, it generally must renumber its network, as the old IP addresses belong to the previous ISP’s allocated block. This is the most common form of addressing for most internet users and businesses. PA addresses are highly efficient for global routing as they allow ISPs to advertise large, aggregated route prefixes via Border Gateway Protocol (BGP)^[4].
Provider-Independent (PI) Addresses: These are IP addresses directly allocated by an RIR to an end-user organization. They are “independent” of any specific ISP. An organization with PI space can multihome with multiple ISPs without renumbering, enhancing network resilience and flexibility. However, PI prefixes are typically smaller than aggregated PA prefixes, meaning they contribute more entries to the global routing table, which can impact routing performance and router memory requirements.

Choosing between PI and PA space involves a trade-off between operational flexibility (PI) and routing efficiency (PA). For most organizations, the simplicity and lower cost associated with PA space outweigh the benefits of PI, especially with the prevalence of NAT (Network Address Translation) for IPv4.

Challenges and Future Trends

The RIR/LIR model faces continuous challenges, particularly with the ongoing IPv4 exhaustion. While LIRs can still obtain small IPv4 allocations in some regions, the primary focus has shifted decisively towards IPv6 adoption.

IPv6 Transition: The vast address space of IPv6 (a /32 LIR allocation alone contains 2^96 addresses) eliminates the scarcity issues of IPv4. However, the transition has been slow, necessitating techniques like dual-stack, NAT64, and DNS64. RIRs and LIRs play a crucial role in promoting and facilitating IPv6 deployment through policies, training, and allocating ample IPv6 resources.
Policy Evolution: RIR policies are constantly evolving to address new challenges. This includes policies for IPv4 transfer markets (allowing organizations to buy/sell unused IPv4 blocks), smaller IPv6 allocation policies for specific use cases, and policies related to routing security.
Routing Security (RPKI): RIRs are instrumental in implementing Resource Public Key Infrastructure (RPKI). RPKI is a framework designed to secure the internet’s routing infrastructure, specifically BGP, by allowing IP address holders (LIRs and end-users with PI space) to cryptographically attest to the legitimacy of their routing announcements. This helps prevent route hijacking and improves the overall stability of the internet^[5]. LIRs are encouraged to generate Route Origin Authorizations (ROAs) for their prefixes to participate in this critical security measure.

Conclusion

The RIR and LIR model is the unsung hero of internet stability and growth. RIRs provide the necessary global coordination and policy framework, while LIRs act as the vital last mile, distributing IP addresses to the vast array of networks that comprise the internet. For technical professionals, understanding this hierarchy is not merely academic; it’s fundamental to designing resilient, scalable, and secure network architectures. As the internet continues to evolve, particularly with the acceleration of IPv6 adoption and the critical need for enhanced routing security, the roles of RIRs and LIRs will remain indispensable in shaping its future.

References

[1] HUSTLER, N. (2020). IPv4 Exhaustion and the Global Routing Table. Available at: https://blog.apnic.net/2020/09/24/ipv4-exhaustion-and-the-global-routing-table/ (Accessed: November 2025)

[2] RIPE NCC. (n.d.). Provider Aggregatable (PA) vs. Provider Independent (PI) address space. Available at: https://www.ripe.net/manage-ips-and-asns/ipv4/pa-vs-pi (Accessed: November 2025)

[3] ARIN. (2023). IPv6 Policy Development. Available at: https://www.arin.net/participate/policy/nrpm/ (Accessed: November 2025)

[4] Cisco. (n.d.). Border Gateway Protocol (BGP) Overview. Available at: https://www.cisco.com/c/en/us/products/routers/what-is-bgp.html (Accessed: November 2025)

[5] IANA. (n.d.). Resource Public Key Infrastructure (RPKI). Available at: https://www.iana.org/assignments/rpki/rpki.xhtml (Accessed: November 2025)