Recherche de numéro d'AS
Qui détient un numéro de système autonome, et chaque préfixe qu'il annonce à la table de routage mondiale.
Rechercher par nom
Saisissez une partie du nom d'un opérateur pour trouver ses numéros d'AS.An autonomous system number identifies one network with its own routing policy — an ISP, a hosting company, a university, a large enterprise. This page shows who holds a given AS number, which registry allocated it, and every IPv4 and IPv6 prefix it announces to the global routing table.
What an AS number is for
The internet is not one network; it is roughly a hundred thousand of them agreeing to carry each other's traffic. BGP is how they agree, and an AS number is how each one is named in that conversation. When your provider announces the prefix containing your address, it does so under its AS number — which is why the origin AS on an address lookup tells you who actually carries your traffic.
Announced prefixes come from the routing table, not the registry
The prefix list here is what the AS is announcing in the global table as of our last rebuild, which is a live operational fact. It is not the same as what the registry allocated to that organisation: networks announce blocks they hold from other parties, sub-allocate to customers, and stop announcing space they still hold. Where an AS is allocated but announces nothing we can see, we say exactly that.
Searching by operator name
Names in the AS registry are inconsistent by nature — the same company appears as a handle, a legal name and a trading name across different records. The name search matches on substrings of both the handle and the organisation field, so a partial name usually finds the right numbers even when the spelling is not the one you expected.
Questions fréquentes
How do I find the AS number of an ISP?
Type part of its name into the search on the ASN page. Large operators hold several AS numbers, often one per country or per business line, so expect more than one result.
What does the number of announced prefixes tell me?
Roughly how much address space the network carries and how finely it slices it. A large ISP announces thousands of prefixes; a single-site enterprise might announce one. A very high count relative to the address total often means the network is announcing many small blocks for traffic engineering.
Why does an AS number show no prefixes?
Either it is allocated but not in use, it is used only for private peering and never appears in the global table, or its announcements are made under a different AS. Allocation and announcement are separate facts and we report them separately.