IP Information: How to Lookup Any IP (GeoIP, WHOIS, ASN, Reverse DNS)
Quickly find geolocation, ISP, ASN, WHOIS records and reverse DNS for any IPv4 or IPv6 address. Use these methods to troubleshoot networking, secure systems, and investigate suspicious activity.
Why IP Information Matters
An IP address is the digital identifier devices use to communicate on networks. Finding IP information helps you:
- Identify geographic origin and approximate location (useful for analytics and blocking fraud).
- Discover ISP and autonomous system number (ASN) for network troubleshooting.
- Lookup WHOIS records to identify ownership of IP ranges.
- Check reverse DNS and open ports when investigating suspicious connections.
What data you can get from an IP lookup
Typical fields returned by an IP information query:
- IP version: IPv4 or IPv6.
- Geolocation: Country, region/state, city, and approximate coordinates.
- ISP & Organization: The provider or owner of the IP.
- ASN: Autonomous System Number and AS name.
- WHOIS: Registered owner of the IP range and contact handles.
- Reverse DNS: PTR record (hostname mapping back to IP).
- Blacklist / Reputation: Any listings on spam or abuse lists.
- Open ports / services: (requires active scanning / consent).
How to perform a quick IP lookup (step-by-step)
Use this practical checklist when you need to investigate an IP.
- Start with a GeoIP lookup to get country, region and city. Try our tool: What's My IP.
- Check WHOIS to find the IP block owner and abuse contact: Hostname To IP.
- Resolve reverse DNS to see the PTR/hostname: IP Subnet Calculator.
- Find ASN & routing to see which network announces the IP: Domain DNS.
- Check DNS & domain context using DNS lookup or domain tools: Domain DNS and Hostname To IP.
- Check reputation against blacklists: Hostname To IP.
- If needed, and only with permission, scan ports to identify exposed services: Ping. (Respect laws & consent.)
Common use cases
IP information is useful for site owners, analysts, and security teams:
- Security investigation: triage login attempts and anomalies.
- Fraud prevention: detect mismatched geolocation on transactions.
- Network troubleshooting: identify transit providers and routing issues.
- Compliance & audit: map assets to jurisdictions and owners.
- Threat intelligence: enrich logs with ASN and blacklist status.
IP Lookup Examples
Example — suspicious login
If a user account shows a login from 203.0.113.45 and your typical logins are from Vietnam:
- Run a GeoIP lookup: is the country different?
- Check WHOIS/ASN: is the IP from a known VPN or hosting provider?
- Check reverse DNS: does the hostname indicate a cloud provider?
- Cross-check blacklist and behavior (multiple rapid logins?).
Example — email spam source
An email header contains 198.51.100.22 — use WHOIS for abuse contact, then check blacklist status and open SMTP ports (with permission).
Privacy, ethics & legal notes
IP data provides approximate location — not precise personal location. Respect privacy and local laws:
- Do not attempt to deanonymize private individuals or perform intrusive scans without explicit authorization.
- Use abuse contacts from WHOIS responsibly if reporting malicious behavior.
- When scanning ports or performing active probes, obtain consent or use your own infrastructure.
Quick reference: recommended mmonestop tools
Use these internal tools for a fast workflow (URLs are example paths; update if your structure differs):
- What's My IP — single-step summary (geolocation, ISP, ASN).
- Hostname To IP — PTR and hostname mapping.
- IP Subnet Calculator — routing & AS owner.
- Domain DNS — spam/abuse reputation.
- Ping — service detection (use responsibly).
Best practices & automation tips
For repeatable investigations:
- Enrich logs at ingestion with GeoIP and ASN so dashboards show context immediately.
- Cache WHOIS results for IP ranges (WHOIS changes rarely) to reduce queries.
- Combine reputation checks with rate-limiting and challenge flows for risky traffic.