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+# ipasn.net DNS API Reference
+
+**Source:** Geoff Huston, APNIC Blog, 2026-02-09
+**URL:** https://blog.apnic.net/2026/02/09/from-the-stupid-dns-tricks-department-ipasn-net/
+
+---
+
+## Overview
+
+`ipasn.net` is a DNS-based IP address enrichment service built on PowerDNS with a plug-in backend. Unlike Team Cymru's `origin.asn.cymru.com`, it accepts IP addresses in natural (non-reversed) order and supports IPv6 addresses with standard colon notation. All queries use DNS TXT record lookups.
+
+The backend assembles responses from three data sources: a current BGP routing table snapshot (origin AS and advertised prefix), a geolocation database (country code), and RIR statistics reports (registry, registration date).
+
+---
+
+## Query Protocol
+
+All queries are issued via `dig +short TXT` (or equivalent DNS TXT lookups).
+
+---
+
+## Endpoints
+
+### 1. Cymru-Compatible (Compact)
+
+Returns a pipe-delimited string similar to Team Cymru's format, but with natural IP address order.
+
+**IPv4:**
+
+```
+dig +short TXT <IPv4_ADDRESS>.origin.asn.ipasn.net
+```
+
+**IPv6:**
+
+```
+dig +short TXT <IPv6_ADDRESS>.origin6.asn.ipasn.net
+```
+
+**Response format:** `"<prefix> | <origin_asn> | <cc> | <rir> | <reg_date>"`
+
+**Example (IPv4):**
+
+```
+$ dig +short TXT 216.88.0.0.origin.asn.ipasn.net
+"216.88.0.0/14 | 3561 | US | arin | 1998-09-25"
+```
+
+**Example (IPv6):**
+
+```
+$ dig +short TXT 2401:2000:6660::.origin6.asn.ipasn.net
+"2401:2000::/32 | 4608 | AU | apnic | 2007-06-19"
+```
+
+---
+
+### 2. Full Detail (Pipe-Delimited)
+
+Returns an extended pipe-delimited record with BGP, registration, org name, and RPKI/ROA data.
+
+```
+dig +short TXT <IP_ADDRESS>.ipasn.net
+```
+
+**Response format (fields separated by `|`):**
+
+| Position | Field | Example |
+|----------|-------|---------|
+| 1 | Queried Address | `216.88.0.0` |
+| 2 | Address Family | `IPv4` or `IPv6` |
+| 3 | BGP Status | `ADVERTISED` |
+| 4 | Advertised Prefix | `216.88.0.0/14` |
+| 5 | Origin AS | `3561` |
+| 6 | Org Name | `CenturyLink_Communications,_LLC` |
+| 7 | Country Code | `US` |
+| 8 | Country Name | `United_States_of_America` |
+| 9 | RIR | `arin` |
+| 10 | RIR Prefix | `216.88.0.0/14` |
+| 11 | Registration Status | `assigned` |
+| 12 | Registration Date | `1998-09-25` |
+| 13 | ROV Status | `VLD` |
+| 14 | ROA Prefix | `216.88.0.0/14` |
+| 15 | ROA Max Length | `24` |
+| 16 | ROA Origin AS | `3561` |
+| 17 | ROA Trust Anchor | `ARIN` |
+
+**Example:**
+
+```
+$ dig +short TXT 216.88.0.0.ipasn.net
+"216.88.0.0|IPv4|ADVERTISED|216.88.0.0/14|3561|CenturyLink_Communications,_LLC|US|United_States_of_America|arin|216.88.0.0/14|assigned|1998-09-25|VLD|216.88.0.0/14|24|3561|ARIN"
+```
+
+---
+
+### 3. JSON Output
+
+Same data as endpoint 2, returned as a JSON object.
+
+```
+dig +short TXT <IP_ADDRESS>.json.ipasn.net
+```
+
+**Response fields:**
+
+```json
+{
+  "Address": "216.88.0.0",
+  "Class": "IPv4",
+  "BGP": "ADVERTISED",
+  "Advertised_Prefix": "216.88.0.0/14",
+  "Origin_AS": "3561",
+  "Org_Name": "CenturyLink_Communications,_LLC",
+  "CC": "US",
+  "CC_Name": "United_States_of_America",
+  "RIR": "arin",
+  "RIR_Prefix": "216.88.0.0/14",
+  "Reg_Status": "assigned",
+  "Reg_Date": "1998-09-25",
+  "ROV": "VLD",
+  "ROA_Prefix": "216.88.0.0/14",
+  "ROA_Maxlen": "24",
+  "ROA_AS": "3561",
+  "ROA_TAL": "ARIN"
+}
+```
+
+Note: The DNS TXT response may span multiple strings that need to be concatenated before JSON parsing.
+
+---
+
+### 4. DNS Resolution + Lookup
+
+Resolves a domain name first, then performs the IP enrichment lookup. Returns full detail format.
+
+**Default (prefers AAAA/IPv6):**
+
+```
+dig +short TXT <FQDN>.dns.ipasn.net
+```
+
+**Force IPv4 (A record):**
+
+```
+dig +short TXT <FQDN>.a.dns.ipasn.net
+```
+
+**Examples:**
+
+```
+$ dig +short TXT www.potaroo.net.dns.ipasn.net
+"2401:2000:6660:0:0:0:0:108|IPv6|ADVERTISED|2401:2000::/32|4608|..."
+
+$ dig +short TXT www.potaroo.net.a.dns.ipasn.net
+"203.133.248.108|IPv4|ADVERTISED|203.133.248.0/24|4608|..."
+```
+
+---
+
+### 5. Individual Attribute Queries
+
+Query a single field by inserting the attribute name before `ipasn.net`.
+
+**Country Code:**
+
+```
+dig +short TXT <IP_ADDRESS>.cc.ipasn.net
+```
+
+Response: `"US"`
+
+**RPKI/ROA Status:**
+
+```
+dig +short TXT <IP_ADDRESS>.rpki.ipasn.net
+```
+
+Response: `"VLD_216.88.0.0/14-24_3561_ARIN"`
+
+---
+
+## Query Pattern Summary
+
+| Query Type | DNS Name Pattern |
+|------------|-----------------|
+| Cymru-compat (IPv4) | `<IPv4>.origin.asn.ipasn.net` |
+| Cymru-compat (IPv6) | `<IPv6>.origin6.asn.ipasn.net` |
+| Full detail | `<IP>.ipasn.net` |
+| JSON output | `<IP>.json.ipasn.net` |
+| DNS resolve (default) | `<FQDN>.dns.ipasn.net` |
+| DNS resolve (force A) | `<FQDN>.a.dns.ipasn.net` |
+| Country code only | `<IP>.cc.ipasn.net` |
+| RPKI status only | `<IP>.rpki.ipasn.net` |
+
+---
+
+## Notes
+
+- IPv4 addresses use natural dotted-quad notation (no octet reversal required).
+- IPv6 addresses use standard colon-delimited notation (no nibble expansion or reversal required).
+- Spaces in org names are replaced with underscores.
+- ROV field values include `VLD` (valid ROA exists). Other possible values are not documented in the source material.
+- The service runs on PowerDNS with a custom backend that dynamically generates responses rather than serving from a zone file.
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