How to retrieve Autonomous System details using WHOIS

Autonomous Systems (AS) are collections of IP networks that share a common routing policy. Each AS is assigned a unique Autonomous System Number (ASN), which is essential for routing traffic across the internet. Network operators, internet service providers (ISPs), and organizations use AS numbers to manage and optimize traffic flow between networks. Understanding ASNs helps network professionals analyze routing policies, diagnose network issues, and track down the organizations behind specific networks.

WHOIS is a protocol used to query databases for information about domain names, IP addresses, and Autonomous Systems. By querying WHOIS, users can access details about the AS, including the organization managing the AS, the assigned IP address ranges, and routing policies. This information is useful for network diagnostics, abuse tracking, and infrastructure analysis.

Querying WHOIS for AS details provides network professionals with insight into internet routing and ownership. WHOIS can return essential data such as AS numbers, IP block allocations, and contact information for network operators. This helps to identify the organizations responsible for specific IP ranges and Autonomous Systems, offering a better understanding of how the internet is structured and maintained.

1. Install a WHOIS client on your system if it's not already available.

   On most Linux distributions, the WHOIS client is pre-installed. For systems without WHOIS, use your package manager to install it.

   $ sudo apt-get install whois

2. Identify the Autonomous System Number (ASN) or the IP address associated with the network.

   You may already know the ASN, or you can start with an IP address to find the ASN.

3. Use the WHOIS command or a web-based WHOIS service to query for AS information.

   $ whois AS15169
   ASNumber:       AS15169
   OrgName:        Google LLC
   OrgID:          GOOGL
   CIDR:           8.8.8.0/24, 8.8.4.0/24

4. If querying by ASN, enter the ASN in the WHOIS command to retrieve detailed information.

   $ whois AS3356
   ASNumber:       AS3356
   OrgName:        Level 3 Parent, LLC
   OrgID:          LVLT
   NetRange:       4.0.0.0 - 4.255.255.255

5. If querying by IP address, input the IP address to find the related ASN and associated details.

   $ whois 8.8.8.8
   NetName:        GOOGLE
   OrgName:        Google LLC
   CIDR:           8.8.8.0/24
   ASNumber:       AS15169

6. Review the results for key information, such as the AS number, IP address ranges, and contact information.

   This output will typically include the ASN, the organization’s name, IP blocks associated with the AS, and routing policies.

7. For more advanced details, query regional internet registries such as ARIN, RIPE, or APNIC.

   Using regional WHOIS databases can give additional details such as specific routing policies or administrative contacts.