IPv4 and IPv6 Resource Queries via RDAP

The Registration Data Access Protocol (RDAP) has fundamentally modernized the way network operators, security professionals, and researchers access internet resource registration data. Among its many capabilities, RDAP provides standardized mechanisms for querying both IPv4 and IPv6 address allocations, offering authoritative information about which organizations hold specific IP address ranges, the status of those resources, and associated contact or administrative details. Unlike the legacy WHOIS protocol, which often returned unstructured and inconsistent results, RDAP delivers this data in a structured, machine-readable JSON format that aligns with current internet governance and security requirements.

IPv4 and IPv6 address space are managed globally by five Regional Internet Registries (RIRs): ARIN, RIPE NCC, APNIC, LACNIC, and AFRINIC. These organizations allocate blocks of IP address space to internet service providers, enterprises, and other registrants. RDAP servers maintained by each RIR expose these allocations via well-defined RESTful endpoints. A query to an RDAP server for an IP address or network prefix returns detailed metadata about that resource, enabling clients to determine the responsible organization, contact points for abuse complaints, administrative entities, and relevant routing or registration events.

When querying an RDAP server with a specific IPv4 or IPv6 address, the server locates the encompassing IP range to which the address belongs. This means that RDAP is not just looking for a match to a single IP but identifies the most specific network allocation that contains the queried address. The response includes the handle or unique identifier of the IP network object, the start and end of the allocated range, and typically one or more status flags indicating whether the block is allocated, assigned, reserved, or available. These status codes are standardized, enabling automated systems to interpret them consistently across different RIRs.

In addition to technical data about the IP block itself, RDAP responses provide critical administrative and operational metadata. Each IP network object may include associated entities such as the organization responsible for the resource, points of contact, and references to related objects like routing information or more specific sub-allocations. The entity objects are typically enriched with vCard-based contact details, including email addresses and phone numbers, which are essential for incident response teams seeking to report abuse, troubleshoot misconfigurations, or coordinate with network operators. For networks associated with large ISPs or multihomed organizations, RDAP responses often include hierarchical references that trace allocations from the RIR to National Internet Registries (NIRs) or Local Internet Registries (LIRs).

For IPv6 queries, RDAP handles the significantly larger address space with the same level of granularity and structure as IPv4. Since IPv6 allocations are typically much larger, often in the form of /32 or /48 prefixes, RDAP is especially valuable in determining the original allocating organization and its intended usage. Whether querying a /128 host address or a broader prefix, the RDAP server responds with the enclosing network object, allowing analysts to determine whether an address is part of a commercial hosting provider, an enterprise internal network, or a public infrastructure block. This contextual information is vital in threat intelligence and network diagnostics, where understanding the source of traffic can inform both policy decisions and technical responses.

RDAP also supports IP network objects with historical event data. Events such as allocation date, last modification, and status changes are included in the response, offering temporal context for analysts. For example, a recently allocated block that suddenly begins generating suspicious traffic may warrant greater scrutiny than a long-standing allocation with a stable reputation. The event records are presented as arrays with timestamped actions such as registration, last changed, or transferred, allowing automated systems to track the lifecycle of the IP resource.

An essential feature of RDAP in the context of IP address queries is the inclusion of links and notices. RDAP responses often contain hypermedia links that point to related entities or authoritative documentation about the resource, such as terms of use or legal disclaimers. These links follow a RESTful architecture that facilitates navigation between related data objects, such as moving from an IP address to its managing organization or to abuse contact points. Notices may also inform clients of redactions, rate limits, or service-level policies, which are particularly important when operating in privacy-conscious environments.

In practical deployment, many RDAP clients are integrated into network security tools, abuse reporting systems, or asset management platforms. These tools automatically query RDAP endpoints when an IP address of interest is observed, such as during firewall log analysis, intrusion detection, or anomaly detection. The structured output allows for seamless enrichment and correlation with other data sources. For instance, a SIEM platform may combine RDAP-derived organization names and abuse contacts with geolocation data and threat intelligence to form a holistic view of suspicious traffic sources.

IPv4 and IPv6 RDAP queries are also instrumental in anti-abuse operations, especially when attempting to distinguish between legitimate service providers and those hosting malicious infrastructure. By examining RDAP data, analysts can determine whether an IP block is owned by a reputable ISP or is part of a transient allocation associated with bulletproof hosting. The accuracy and timeliness of RDAP responses, maintained directly by RIRs and often updated in near-real-time, ensure that decisions based on RDAP data reflect the current operational landscape of internet resource allocations.

Overall, RDAP has elevated the process of querying IP resource information to meet the demands of automation, compliance, and cyber defense. Its structured data model, support for both IPv4 and IPv6, and integration-friendly architecture make it an indispensable tool for anyone seeking to understand the ownership, status, and operational context of internet address space. As the global transition to IPv6 continues and networked systems become more complex, the role of RDAP in maintaining transparency and accountability in IP address management will only become more critical.

The Registration Data Access Protocol (RDAP) has fundamentally modernized the way network operators, security professionals, and researchers access internet resource registration data. Among its many capabilities, RDAP provides standardized mechanisms for querying both IPv4 and IPv6 address allocations, offering authoritative information about which organizations hold specific IP address ranges, the status of those resources, and…