IP Addresses, ASNs & Geolocation: The Complete Guide
An IP address identifies a device's location on a network, but what an IP lookup actually reveals — geolocation, ISP, and the Autonomous System Number (ASN) behind it — is more nuanced and more limited than most people assume. This guide covers what an ASN actually identifies, how accurate (and inaccurate) IP geolocation really is, why it can never point to a specific person, and how to genuinely verify a crawler claiming to be Googlebot rather than trusting its User-Agent header alone.
What an IP lookup can actually tell you
For any IP address, a lookup can surface three genuinely useful things: its approximate geolocation (country reliably, city as a best estimate), the ISP or hosting provider operating that IP range, and the Autonomous System Number (ASN) — the network operator that controls routing for that block. It cannot tell you a person's name, street address, or any detail tied to a specific individual — IP-based lookups only ever resolve to network- and organization-level information, never to a person, regardless of what a tool's marketing might imply.
Autonomous System Numbers: the identity that doesn't drift
An ASN identifies a single network operator — an ISP, cloud provider, university, or company — that independently controls how traffic routes to and from its own IP address ranges. Google's public-facing services, for example, sit behind AS15169. The ASN is worth checking specifically because it's more reliable than a plain organization-name field: that name can be outdated, inherited from a reseller arrangement, or simply generic, while the ASN is the actual registered routing identity maintained with the relevant regional internet registry (ARIN, RIPE, APNIC, and others) and doesn't drift the way free-text fields can.
Why geolocation accuracy varies so much by connection type
Country-level geolocation is generally reliable, because IP address blocks are allocated in ways that closely track national and regional registries. City-level is a best estimate, not a precise measurement, and its reliability depends heavily on the type of connection:
- Home broadband — often reasonably accurate at the city level, since residential ISP IP blocks tend to map to real regional infrastructure.
- Mobile networks — frequently inaccurate, since traffic routes through a carrier's regional hub rather than reflecting the phone's actual physical location at that moment.
- VPNs — will report the VPN exit server's location by design, which is the entire point of using one, not a flaw in the geolocation.
- Cloud and hosting IPs — report a data center's location, which may be in an entirely different region or country from wherever the actual service or user is.
| Connection type | City-level accuracy | Why |
|---|---|---|
| Home broadband | Often reasonably accurate | Residential IP blocks map to real regional infrastructure |
| Mobile networks | Frequently inaccurate | Routes through a carrier's regional hub, not the phone's actual location |
| VPN | Reports the exit server | By design — that's the point of a VPN |
| Cloud / hosting | Reports the data center | May be a different region/country than the real user |
Why geolocation can never identify a person
This is worth stating plainly because it's commonly overestimated: an IP lookup resolves to a network operator and, at best, an approximate city — never a specific person, household, or street address. Tying an IP address to an actual individual requires a legal process compelling the ISP itself to disclose its own private subscriber records, something entirely outside what any public IP or ASN lookup tool has access to or was ever designed to provide.
Verifying a crawler is genuinely Googlebot, not a spoofed User-Agent
Anyone can set their browser's or script's User-Agent header to literally say "Googlebot" — the header itself proves nothing. A useful first check is confirming the request's source IP resolves to an ASN Google actually owns (AS15169, or a small number of other Google-registered ASNs) rather than an unrelated hosting provider; a mismatch is an immediate red flag. That check alone isn't a complete verification, though — Google's own documented method is a reverse-DNS lookup on the IP to confirm it resolves to a .googlebot.com, .google.com, or .googleusercontent.com hostname, followed by a forward-DNS lookup on that hostname to confirm it maps back to the original IP. The ASN check is a fast first pass; the DNS round-trip is the actually authoritative method when it matters (like deciding whether to serve different content or block a request outright).
Public vs. private IP addresses
A public IP is globally unique and is exactly what other servers see when your device connects to them — the address an IP lookup tool reports. A private IP (ranges like 192.168.x.x, 10.x.x.x, and 172.16.x.x through 172.31.x.x) only has meaning inside a local network and is never directly reachable from the public internet; a router's NAT (Network Address Translation) maps every device on a home or office network to one shared public IP for anything leaving that network.
| Public IP | Private IP | |
|---|---|---|
| Uniqueness | Globally unique | Reused across countless local networks |
| Reachable from the internet? | Yes | No |
| Example ranges | Everything not reserved as private | 192.168.x.x, 10.x.x.x, 172.16–31.x.x |
| What an IP lookup tool sees | This | Never this directly |
Frost Rank's IP Address Lookup detects and displays your own public IP automatically, alongside full geolocation, ISP and ASN lookups for any other IP or AS number.
Frequently asked questions
An ASN identifies the network operator that controls routing for a block of IP addresses, such as AS15169 for Google. It's more reliable than an organization name, which can be outdated or generic. See why the ASN is the better signal.
Country-level is generally reliable; city-level is a best guess that is often close on home broadband but often wrong for mobile, VPN and cloud IPs. See accuracy by connection type.
No. It resolves to a network and at best an approximate city; linking an IP to a person takes a legal request to the ISP. See why an IP can't identify a person.
Check that the IP belongs to a Google ASN as a quick first pass, then confirm with a reverse DNS lookup to a googlebot.com or google.com hostname and a forward lookup back to the same IP. See the full verification steps.
A public IP is globally unique and is what other servers see; a private IP, like 192.168.x.x, only works inside a local network behind a router's NAT. See public and private IPs compared.
Registry data (who owns an IP range, which ASN it belongs to) changes infrequently — typically not more than a few times a year for any given block — so caching results for a short window (commonly 15–30 minutes) avoids hammering the underlying registry APIs with repeat lookups for the same IP without meaningfully sacrificing accuracy, since the answer almost never changes between one lookup and the next within that window.
The Googlebot verification method and ASN behavior described above match Google's own documented crawler-verification process and the real registry data Frost Rank's IP Address Lookup queries — not a simplified approximation.
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