ASN Converter
Enter an ASN in any format and I show its asplain ↔ asdot equivalence, whether it is 16- or 32-bit and whether it is public, private or reserved (0, 23456 AS_TRANS, etc.).
asdot breakdown · high.low
| Part | Decimal | Formula |
|---|
How it is computed · asplain, asdot and ranges
1. An ASN is an unsigned
32-bit integer: from 0 to
4294967295 (2³² − 1).
2. asdot+ splits it in two:
high = ⌊asn / 65536⌋ and low = asn mod 65536,
written as high.low.
3. asdot is the short form:
equal to asplain when the ASN is < 65536
(16-bit); otherwise it is high.low. E.g. 65546 →
1.10.
4. 16-bit: 0–65535.
32-bit: 65536 and up.
Private: 64512–65534 (16-bit)
and 4200000000–4294967294 (32-bit).
5. Reserved:
0, 23456 (AS_TRANS),
65535, 4294967295,
documentation (64496–64511 and 65536–65551).
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How it works
The converter takes an autonomous system number (ASN) in any notation —asplain (integer from 0 to 4294967295), asdot (for example 1.10) or with the AS prefix— and shows its three representations, whether it is 16-bit or 32-bit, and the high.low breakdown: high = ⌊asn ÷ 65536⌋ and low = asn mod 65536. The asdot notation is the short form (equal to asplain below 65536); asdot+ always carries the dot.
It also classifies the ASN according to the IANA registries: private if it falls in 64512-65534 (16-bit) or 4200000000-4294967294 (32-bit) per RFC 6996, reserved if it is 0 (RFC 7607), 23456 (AS_TRANS, RFC 6793), 65535, 4294967295 or within the documentation ranges 64496-64511 and 65536-65551 (RFC 5398), and public (assignable by an RIR) in every other case.
Example: what ASN is 1.10 in asplain?
- In asdot,
1.10means high = 1 and low = 10. - asplain:
1 × 65536 + 10 = 65546. - Since 65546 ≥ 65536, it is a 32-bit ASN; and since it falls in 65536-65551, it is reserved for documentation (RFC 5398).