Free tool
DNS & lookupReverse DNS Lookup
Convert a public IP address into its PTR hostname. Confirm reverse DNS for mail servers, labs, and troubleshooting.
Looks up public internet data for the target you enter. We do not store results.
Free toolForward DNS turns names into IPs. Reverse DNS turns IPs back into names through PTR records. This free reverse DNS lookup helps CCNA students and network engineers confirm which hostname a public IPv4 address claims, which matters for email reputation, logging, and Cisco networking labs. After you map an address into a CIDR block during subnetting practice, check its PTR here to complete the picture.
How to use the Reverse DNS Lookup
- 1
Enter a public IPv4 or IPv6 address (private ranges are blocked).
- 2
Tap Lookup PTR to request the reverse DNS hostname.
- 3
Compare the PTR name with the forward A or AAAA record for that host to confirm they match.
Why reverse DNS matters in real networks
Mail gateways often reject or throttle senders whose PTR record is missing or does not match the HELO name. Network administration teams also use reverse DNS when they read logs that only show IPs. Home networks rarely publish PTR records on public space you do not control, but students still need to read PTR answers on public resolvers such as 8.8.8.8 during CCNA study.
Reverse DNS IPv4 example
Look up 8.8.8.8. You should see a Google public DNS hostname such as dns.google. That is a classic IPv4 reverse DNS example used in classrooms and helpdesk drills.
Guides and next steps
Privacy note
We query public reverse DNS for the IP you submit. Private and reserved addresses are blocked. We do not store lookups.
Frequently asked questions
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