Network · BGP
AS number range classifier.
Enter an AS number as asplain (4200000001) or asdot+ (64086.59905). Get both notations and whether the number sits in a private-use, documentation, AS_TRANS or reserved range. It classifies the number only; nothing leaves your browser.
AS number
Result
Enter an AS number, then press Classify.
asplain and asdot+
An AS number is a 32-bit value. asplain writes it as one decimal integer, for example 65536. asdot+ writes the high 16 bits, a dot, then the low 16 bits, for example 1.0. The conversion is: high = floor(n / 65536), low = n mod 65536. RFC 5396 recommends asplain, and the IANA registry uses it.
Special-purpose AS number ranges
0— reserved (RFC 7607)23456— AS_TRANS, the 16-bit placeholder for 32-bit numbers (RFC 6793)64496-64511and65536-65551— documentation and sample code (RFC 5398)64512-65534and4200000000-4294967294— private use (RFC 6996)65535and4294967295— reserved (RFC 7300)65552-131071— reserved in the IANA registry
Sources: IANA Autonomous System (AS) Numbers registry (last updated 2026-06-01) and RFC 5396, both read 2026-09-30.
Frequently asked questions
Does "not in a special range" mean the ASN is assigned?
No. This tool classifies the number against the reserved, documentation and private-use ranges only. It has no Regional Internet Registry data, so it cannot tell you whether a number has been assigned, or to whom. Search the registries for that.
What is the private ASN range?
Two blocks: 64512-65534 (16-bit) and 4200000000-4294967294 (32-bit), per RFC 6996. They are not globally unique and should not be announced to the public Internet.
Why is there no plain asdot?
Plain asdot writes numbers below 65536 as integers and larger ones as high.low. Those small numbers are the same in asplain, and the larger ones match asdot+, so this tool shows asplain and asdot+ only.
Range check only
This confirms the format and range of an AS number. It does not confirm the number was issued to any network. Everything runs in your browser and nothing you type is sent to any server.