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ASN Lookup

ASN Lookup tool tells the ASN WHOIS details. Just enter the AS number and find which company is using that ASN and what the origin of that company is. i.e., country, city, latitude, longitude, state, etc.

About ASN Search Tool - Perform ASN Lookup

The ASN search tool quickly looks up Autonomous System Number (ASN). Enter the AS number, find which company uses that ASN, and more.

What is AS number lookup?

AS number lookup or ASN lookup querying the different RIR databases to get information about the ASN. From the ANS checker, you can grab the following information, such as

  • AS-Block
  • Description
  • Mnt-by
  • Creation and last-update date
  • Source of the ASN information
  • Responsible organization
  • Aut-Num
  • Admin, Technical, and Abuse contact information
  • ASN Status
  • AS Name

How to use AS number lookup to find WHOIS information about an ASN?

ASN is generally the same for all IPs of any organization, network operator, or domain with the same and clear external routing policy.

The specific ASN can be allowed or denied access to any network with policy-based routing.

To perform the autonomous system number lookup for ASN WHOIS, perform the following steps.

  • Open the ASN Lookup
  • Enter the ASN. Or, if you do not know the IP address, perform the IP address lookup to get its ASN.
  • Enter the ASN and click on the "Lookup ANS" button.
  • The tool will perform the ASN Lookup and provide the WHOIS information of provided ASN.
  • The information helps find the assigned owner, location, contact information, and abuse reporting details for provided ASN.

What is an autonomous system?

The internet world is a network of networks. Autonomous systems are the extensive networks that make up the internet.

In simple words, the autonomous system (AS) is the network or the group of networks with a SINGLE and CLEARLY DEFINED routing policy. So if the autonomous systems have to communicate with each other, they need a unique number or identifier.

Each autonomous system (AS) assigns a unique autonomous system number (ASN), a unique globally available identifier. It allows its AS to exchange routing information with other systems.

Consider an AS as a town's post office. The mail moves from one office to another until it reaches the proper town, and that town's post office is responsible for delivering it to the correct destination.

Similarly, the data packets move from one AS to another until it reaches the proper AS containing the destination IP address. The routers within the AS send that packet to the destined IP address.

Different types of autonomous systems

Three types of autonomous systems need an autonomous system number (ASN).

  • Multihomed: Connected to more than one autonomous system (AS)
  • Stub: Connected to only one other autonomous system (AS)
  • Transit: That provides the connections through itself. It links two or more autonomous systems, allowing data to pass through them, even data from unassociated networks.

What is IP address space in an autonomous system?

Each device on the internet has a unique numerical address called an IP address. It's like your identification number on the internet. One from check my IP tool can get its device IP assigned to it by its ISP and locate its location from the IP location finder.

Every AS controls a specific set of IP addresses. Just like the town's post office, which is responsible for delivering the post to all the addresses within its territory. IP address space is the range of IP addresses over which an AS has control. More specifically, you can also call it an IP block.

When the network engineers communicate which IP addresses are controlled by which AS, they do so by talking about the IP address prefixes owned by each AS. An IP address prefix is the range of IP addresses represented in that fashion:

Suppose a company, XYZ, operates AS and owns a range of IP addresses that include an IP If the computer sends a packet to IP, it will eventually reach the AS operated by XYZ.

If that first computer sends a packet to IP address, the packet will move to a different AS.

Note: For reaching its destined IP address (, the packet may even have to pass through the AS operated by XYZ.

What is an autonomous system number (ASN)?

Each AS is assigned an official number, which is a unique identifier. It's globally available and allows its AS to exchange routing information with other systems.

The Autonomous system number (ASN) can be public or private.

  • The public ASN is required to exchange information on the internet.
  • The private ANS is needed if a system communicates through Border Gateway Protocol (BGP) solely with a single provider.

The ASNs were introduced to regulate networking organizations such as Internet Service Providers (ISP), government agencies, and educational institutions.

Autonomous system number formats

Till 2007, all autonomous system numbers were 2 bytes (16-bit). That gave Internet Assigned Numbers Authority (IANA) 65,536 possible ASNs to distribute. The IANA has reserved 1,023 ASNs (64,512 to 65,534) for private use.

But just like IPv4, these were also destined to run out. Just like the creation of IPv6, created 4-byte (32-bit) ASNs to overcome that issue. That gave IANA 4,294,967,296 possible ASNs to distribute. The IANA has reserved 94,967,295 ASNs (4,200,000,000 to 4,294,967,294) for private use.

How to obtain an autonomous system number (ASN)?

Obtaining an autonomous system number (AS) requires the company or other party to submit a petition to the IANA through one of five global Regional Internet Registries or RIRs. The Regional offices are established for Africa, America, Asia, Latin America, the Caribbean, and Europe.

For example, to qualify for the ASN, an organization must have either.

  • Unique routing policy and need to interconnect with another AS.
  • Or the organization is currently multihomed.

Follow the procedure provided by ARIN for requesting an ASN if you lie in their regional territory.

Note: There is a limited number of ASNs available. And if the governing bodies provide ASNs too freely, the supply would run out, and routing becomes more complex.

How do autonomous systems connect?

Autonomous systems connect and exchange network traffic through a process called peering. Autonomous systems peer together by connecting at physical locations called Internet Exchange Points (IXPs).

How can autonomous system numbers (ASN) benefit your business?

  • It increases the flexibility of your network and provides flexible network management.
  • Using your ASN and IP address improves the portability of IP addresses.
  • It helps in direct peering with different Internet Exchange points.
  • It helps in greater traffic control.
  • Network operators can get their network identity, both externally and internally.
  • Provides the capability to establish your BGP using a public ASN.

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