A reverse IP lookup is a technique used to identify hostnames or domain names associated with a specific IP address by querying DNS pointer (PTR) records. This process is the inverse of a standard DNS lookup, where a domain name is resolved to an IP address. Reverse IP lookups are commonly used to determine the hostname linked to an IP address, which can be helpful in network troubleshooting, security investigations, and email deliverability checks.
The lookup works by searching for PTR records in the DNS system, which map an IP address to a domain name. For IPv4 addresses, the reverse lookup typically uses the in-addr.arpa domain, while IPv6 addresses use ip6.arpa. If a PTR record exists for the IP address, the reverse lookup will return the associated hostname; however, not all IP addresses have such records, so results may be absent.
Reverse IP lookups are particularly useful in identifying virtual hosts sharing the same IP address, a common practice in shared web hosting environments. This can help security professionals expand the attack surface during reconnaissance by discovering potentially less secure websites hosted on the same server as a primary target. Additionally, it can assist in identifying spam sources, tracking malicious activity, or checking the reputation of websites hosted on the same server.
Several tools and methods are available for performing reverse IP lookups. On Linux and Unix-like systems, commands such as nslookup, dig, and host can be used. For example, the nslookup command can be run with an IP address to retrieve the associated hostname. On Windows, the nslookup command-line utility is commonly used for reverse DNS lookups. Additionally, online tools like HackerTarget.com, WhatIsMyIP.com, MXToolbox, and NordVPN offer free reverse IP lookup services to find domains associated with an IP address.
Some services also support bulk queries or API access for large-scale operations, such as querying entire CIDR blocks (up to /24) or retrieving up to 10 million results via an API. These tools are valuable for security analysts, network defenders, and researchers conducting open-source intelligence (OSINT) investigations.
What's your go-to for finding IP address information?
Reverse Lookups
These are both private services but the absolute best 2 are:
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Farsight DNSDB (http://dnsdb.info) [Free for independent researchers, expensive comercially]
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DomainTools (http://domaintools.com) [No free plans, and quite expensive if you're independent]
Reverse IP Lookup Tool
What's your go to resource for finding IP address information?
Videos
ping -a w.x.y.z
Should resolve the name from the IP address if the reverse lookup zone has been set up properly. If the reverse lookup zone does not have an entry for the record, the -a will just ping without a name.
nslookup <ip>
Does what you're looking for. It will tell you the server you're querying and the result.
For example:
c:\>nslookup 192.168.101.39
Server: dns1.local
Address: 192.168.101.24
Name: enigma.local
Address: 192.168.101.39