Where's Waldo Library? Using Reverse IP Geolocation to Identify Library IPs

2026-05-28

AI Summary

This study addresses the lack of systematic records linking community anchor institutions—such as public libraries—to their IP addresses, which hinders large-scale assessment of their internet service quality. To overcome this gap, the authors propose a reverse IP geolocation framework that integrates libraries’ publicly available physical addresses with multiple sources of network data, including commercial IP geolocation databases, DNS PTR records, WHOIS information, and broadband provider datasets. The approach is validated through active network measurements and successfully maps approximately 50% of U.S. public libraries to their corresponding IP prefixes. This mapping spans all 50 states and encompasses both urban and rural areas, establishing a scalable and reproducible foundation for remote broadband performance evaluation at anchor institutions nationwide.

Abstract

Community anchor institutions (CAIs), such as libraries, schools, and community centers, are critical for providing Internet access to un- or under-served individuals and communities. Because many of these institutions are themselves under-provisioned, analyzing the reliability and quality of their Internet service is important. Doing so at scale requires knowing the IP addresses of these institutions so that broadband measurement and policy evaluation can occur. Unfortunately, these IPs are not systematically documented. As a first step towards widespread, scalable evaluation of CAI Internet connectivity, this paper presents Reverse IP Geolocation (RG), a new framework to infer IP addresses from physical address data. A key insight is that CAI street addresses are publicly known, which allows us to identify a candidate set of IPs from commercial geolocation that are likely serving the location associated with a CAI. In this paper, \textbf{we focus on US public libraries}, which offer both geographic diversity across thousands of locations, and some publicly available institutional records (\eg{}WHOIS registrations) that enable systematic validation of our approach. Our approach offers a novel integration of IP geolocation databases, DNS PTR records, WHOIS registrations, broadband provider data, and active measurements to identify IPs likely assigned to libraries and validate them. Based on evaluations, our approach can map a library to its IP prefix approx. half of the time, with coverage across all US states, as well as urban and rural areas. Our results highlight the feasibility of mapping CAI presence in IP space and offer a foundation for large-scale, remote broadband infrastructure evaluation.

Problem

• Community Anchor Institutions
• IP Address Identification
• Reverse IP Geolocation
• Public Libraries
• Internet Connectivity

Innovation

• Reverse IP Geolocation
• Community Anchor Institutions
• IP Mapping
• Public Libraries
• Broadband Measurement