Glossary · Networking
Reverse DNS
The lookup that turns an IP address back into a hostname, often the most telling single fact about who operates an address.
Forward DNS turns a name into an address; reverse DNS does the opposite, resolving an address to the hostname its operator has published for it through a PTR record. Not every address has one, but when it does, that name frequently says more than the network registration alone.
The reason it is useful is that operators name their machines by pattern. A hosting provider labels servers by region and instance type, so a PTR record can expose a datacenter address that was trying to look residential. A home connection usually carries its ISP's own naming, which reads very differently. The presence or absence of a record is itself a signal, and detection systems weigh it accordingly.
No single lookup is proof. A PTR record is set by whoever controls the address and can be anything they choose, so it is one input among several, read alongside the network, the geolocation and the address's history rather than trusted on its own.
How HProxy handles it
Where we hold a reverse DNS record for an address we show it on that address's page, because for tracing an IP found in a log it is often the single most specific fact available: no two addresses share a hostname, unlike a network name that covers thousands.
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