# 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.