IPv4 Glossary
Key terms and definitions for IPv4 addressing, networking protocols, RIR operations, and the IPv4 transfer market.
IPv4 Glossary
AFRINIC
The Regional Internet Registry for Africa, responsible for allocating IP address resources in the African region.
APNIC
The Regional Internet Registry for the Asia Pacific region, managing IP address allocation across Asia and Oceania.
ARIN
The American Registry for Internet Numbers, the RIR responsible for IP address management in the United States, Canada, and several Caribbean and North Atlantic islands.
ASN (Autonomous System Number)
A unique identifier assigned to a network or group of networks under a single administrative domain for BGP routing on the internet.
Anycast
A network addressing method where the same IP address is announced from multiple locations. Traffic is automatically routed to the nearest announcing node, commonly used for DNS servers and CDN infrastructure.
BGP (Border Gateway Protocol)
The routing protocol used to exchange routing information between autonomous systems on the internet, determining how IP traffic flows between networks.
Blacklist
A database of IP addresses identified as sources of spam, malware, or other malicious activity. Being blacklisted can affect email deliverability and network reputation.
Check IP Blacklist StatusBogon
An IP address or prefix that should not appear in internet routing tables. Bogon addresses include unallocated IP space, private RFC 1918 addresses, and reserved ranges. Bogon filtering is a security best practice.
CIDR (Classless Inter-Domain Routing)
A method of IP address allocation that replaces the older class-based system, using slash notation (e.g., /24) to define network size.
Due Diligence
The investigation and verification process performed before an IPv4 transaction, including blacklist checks, BGP history review, and ownership verification.
DNSBL (DNS-based Blackhole List)
A DNS-based system for publishing lists of IP addresses associated with spam or abuse. Mail servers query DNSBLs to decide whether to accept or reject incoming messages. Common DNSBLs include Spamhaus, SORBS, and Barracuda.
Check IP BlacklistDual Stack
A network configuration where devices and interfaces run both IPv4 and IPv6 simultaneously. Dual stack is the most common transition strategy, allowing gradual migration to IPv6 while maintaining IPv4 connectivity.
IPv4 vs IPv6Escrow
A financial arrangement where a third party holds funds during a transaction until all conditions are met, commonly used in IPv4 purchases for buyer and seller protection.
Geofeed
An RFC 8805 standard file format that allows IP address holders to publish geolocation data for their IP ranges, helping improve IP geolocation accuracy.
Geofeed Generator ToolInter-RIR Transfer
The transfer of IPv4 addresses between organizations registered under different Regional Internet Registries.
Intra-RIR Transfer
The transfer of IPv4 addresses between organizations registered under the same Regional Internet Registry.
IPv4 (Internet Protocol version 4)
The fourth version of the Internet Protocol, using 32-bit addresses (e.g., 192.168.1.1). The global IPv4 address pool has been exhausted since 2011, creating a secondary market for trading addresses.
Browse IPv4 MarketplaceIPv4 Broker
A company or individual that facilitates IPv4 address transactions between buyers and sellers, handling contracts, due diligence, and RIR transfer processes.
About ipv4.centerIRR (Internet Routing Registry)
A distributed database system where network operators register their routing policies and route announcements. IRR objects (such as route objects and aut-num objects) help other networks verify and filter BGP announcements for security and accuracy.
IPv4 Exhaustion
The depletion of the global pool of unallocated IPv4 addresses. All five RIRs have exhausted their free pools, making the secondary market the primary source for acquiring IPv4 space.
IPv4 Waiting List
A queue maintained by some RIRs (notably RIPE NCC) where organizations can register to receive IPv4 address space from returned or recovered blocks. Wait times vary significantly and allocations are typically small (/24).
IPv6 (Internet Protocol version 6)
The successor to IPv4, using 128-bit addresses to provide a virtually unlimited address space. IPv6 adoption is growing but IPv4 remains essential for most internet operations.
LACNIC
The Regional Internet Registry for Latin America and the Caribbean, responsible for IP address allocation in the region.
LIR (Local Internet Registry)
An organization (typically an ISP or large enterprise) that has been allocated IP address space by a Regional Internet Registry. LIRs can assign addresses to their customers and may transfer allocated space according to RIR transfer policies. In the RIPE NCC region, becoming an LIR member is the standard way to obtain and manage IP resources.
Buy IPv4 AddressesLRSA (Legacy Registration Services Agreement)
An agreement offered by ARIN to holders of legacy IPv4 address space (allocated before the RIR system). Signing an LRSA brings legacy resources under ARIN's policies, enabling transfers through ARIN's transfer system.
LACNIC (Latin America and Caribbean Network Information Centre)
The Regional Internet Registry for Latin America and the Caribbean, responsible for IP address allocation in the region.
Legacy IPv4 Space
IPv4 address blocks that were allocated before the Regional Internet Registry system was established (prior to 1997). Legacy holders may need to sign a Legacy Registration Services Agreement (LRSA) with their RIR before transferring these resources.
ARIN Transfer GuideLOA (Letter of Authorization)
A formal document authorizing a lessee to use and announce specific IPv4 address blocks, typically provided in IPv4 lease agreements.
Lease IPv4 AddressesNAT (Network Address Translation)
A technique that allows multiple devices on a private network to share a single public IPv4 address. NAT is widely used to conserve IPv4 address space but can complicate peer-to-peer connectivity and certain applications. NAT is generally not needed in IPv6 networks.
Needs-Based Justification
A requirement by some RIRs (notably ARIN under Policy 8.3) that transfer recipients demonstrate a legitimate need for the IPv4 addresses, typically through a 24-month network utilization plan. RIPE NCC removed this requirement in 2014 under RIPE-689.
ARIN Transfer GuidePA (Provider Aggregatable) Space
IPv4 address space assigned to an end user by a Local Internet Registry (LIR) or ISP. PA space is typically registered under the provider's account and may need to be returned if the customer changes providers. Transfer rules for PA space vary by RIR.
PI (Provider Independent) Space
IPv4 address space assigned directly to an end user organization by a Regional Internet Registry. PI space is portable — it stays with the holder regardless of which ISP they use. PI allocations are common in the RIPE NCC region.
Prefix
An IPv4 address block defined by a network address and subnet mask, expressed in CIDR notation (e.g., 192.0.2.0/24 represents 256 addresses).
RIR (Regional Internet Registry)
Organizations responsible for managing and allocating IP address resources in specific geographic regions. The five RIRs are RIPE NCC, ARIN, APNIC, LACNIC, and AFRINIC.
RIPE NCC
Réseaux IP Européens Network Coordination Centre, the RIR for Europe, the Middle East, and parts of Central Asia. RIPE NCC handles the most active IPv4 transfer market.
ROA (Route Origin Authorization)
A cryptographically signed object in RPKI that authorizes an autonomous system to originate routes for specific IP prefixes, helping prevent route hijacking.
RPKI (Resource Public Key Infrastructure)
A security framework for internet routing that provides a way to connect IP address blocks to their legitimate holders using digital certificates.
Subnet
A logical subdivision of an IP network, identified by a range of IP addresses. Common subnet sizes include /24 (256 IPs), /23 (512 IPs), /22 (1,024 IPs), and /16 (65,536 IPs).
View Subnet PricingSWIP (Shared WHOIS Project)
A process used primarily in the ARIN region for recording the reassignment or reallocation of IP address blocks to downstream customers. SWIP updates the WHOIS database to reflect who is actually using the addresses.
Transfer Policy
The rules and procedures established by each RIR governing how IPv4 address blocks can be transferred between organizations.
WHOIS
A query and response protocol used to look up registration information for IP addresses, domain names, and autonomous system numbers. WHOIS databases are maintained by RIRs and domain registries.
WHOIS Lookup ToolUnderstanding the IPv4 Ecosystem
The IPv4 address market involves multiple stakeholders, registries, and technical protocols. This glossary covers the essential terminology you need to navigate it confidently.
Ready to Enter the IPv4 Market?
Now that you know the terminology, explore our marketplace to buy, sell, or lease IPv4 addresses with confidence.