↩️ Reverse DNS Lookup
Find the hostname associated with an IP address by querying PTR records. Verify forward-confirmed reverse DNS (FCrDNS).
What is Reverse DNS?
Reverse DNS (rDNS) maps an IP address back to a hostname. Unlike forward DNS which resolves domain names to IP addresses, reverse DNS does the opposite — it finds the domain name associated with a given IP address by querying PTR records.
What is FCrDNS?
Forward-Confirmed reverse DNS (FCrDNS) is a verification method where the hostname obtained from a reverse DNS lookup is resolved forward again to check if it points back to the original IP address. FCrDNS verification is commonly used by mail servers to detect spoofing and by security tools to validate host identity.
Common Uses
| Use Case | Description |
|---|---|
| Email Delivery | Mail servers check rDNS to verify sender legitimacy and reduce spam |
| Security Auditing | Identify the owner or operator of an IP address in logs |
| Network Troubleshooting | Determine which hostname is associated with a network endpoint |
| Anti-Spam Filtering | FCrDNS verification helps filter connections from spoofed hosts |