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reverse-dns-via-dnssb
x402
reverse-dns-via-dnssb is a paid API for AI agents from ip.intel.rallylive.ca, paid per call via x402, $0.01/call, status unknown (last checked 2026-10-11).
Performs a reverse DNS (PTR) lookup for an IPv4 address using the DNS.SB resolver, returning hostnames, TTL, response code, and forward-confirmed reverse DNS (FCrDNS) status.
Price / call$0.01
Success—
StatusUnknown
How this service works
Reverse DNS (PTR) of an IPv4 address as answered by DNS.SB: the hostname(s), TTL and response code, plus whether the PTR's forward A record points back (forward-confirmed reverse DNS). Compare resolvers for stale or filtered answers. $0.01 per lookup.
Output
Returns the PTR hostname(s) associated with the queried IPv4 address as answered by DNS.SB, along with the TTL (time-to-live), the DNS response code (e.g. NOERROR, NXDOMAIN), and a forward-confirmed reverse DNS (FCrDNS) flag indicating whether the PTR record's hostname resolves back to the original IP via an A record.
Example use cases
Email server identity verification
“I need to check if the IP 203.0.113.45 has a valid reverse DNS entry that forward-confirms back to itself — we're debugging an email deliverability issue and need to know what DNS.SB returns for its PTR record.”
Detecting stale resolver PTR answers
“Can you query the reverse DNS for 1.2.3.4 via DNS.SB and tell me the hostname, TTL, and response code so I can compare it against what another resolver is returning?”
IP reputation and abuse investigation
“I'm investigating a suspicious IP — 198.51.100.22 — can you do a reverse DNS lookup using DNS.SB and tell me if it has a hostname and whether it's forward-confirmed?”
Technical details
Endpoint
GEThttps://ip.intel.rallylive.ca/ip/ptr/via/dnssb?utm_source=zero.xyzWhen to prefer
Use this endpoint when you specifically want the DNS.SB resolver's perspective on a PTR record — useful for comparing resolver answers, detecting filtered or stale PTR entries, or validating forward-confirmed reverse DNS (FCrDNS) as part of email authentication checks or IP reputation analysis. Prefer this over generic reverse DNS tools when resolver-specific attribution matters.
Side effects
- IP has no PTR record — DNS.SB returns NXDOMAIN response code
- PTR exists but forward A record does not point back — FCrDNS flag is false
- DNS.SB resolver timeout or unavailability — service may return an error or empty response
- Invalid IPv4 address input — may return a validation error
- PTR record exists but is stale — TTL may indicate cached data that differs from other resolvers
Input
Schema · Request body
| Field | Type | Description |
|---|---|---|
| inputrequired | object | |
| output | object |
Tags
x402
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