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What is nslookup and how does it work?

Published in Computer Networking 2 mins read

nslookup is a command-line tool used to query the Domain Name System (DNS) for information about domain names and their corresponding IP addresses. It's a valuable tool for network administrators and anyone interested in understanding how DNS works.

Here's how nslookup works:

  1. You enter a domain name: For example, you might type nslookup google.com.
  2. nslookup sends a query: The tool sends a DNS query to a DNS server, usually the one configured on your system.
  3. DNS server responds: The DNS server receives the query, looks up the domain name in its database, and returns the corresponding IP address and other information.
  4. nslookup displays the results: The tool displays the results of the query, including the IP address, hostname, and other relevant information.

Here are some practical uses of nslookup:

  • Verify DNS records: You can use nslookup to check if DNS records are correctly configured for a domain name.
  • Troubleshoot DNS issues: If you're experiencing issues with DNS resolution, you can use nslookup to identify the source of the problem.
  • Find IP addresses: You can use nslookup to find the IP address of a specific website or server.
  • Learn about DNS servers: You can use nslookup to identify the DNS servers used by your computer or network.

Example:

C:\> nslookup google.com
Server:  192.168.1.1
Address:  192.168.1.1

Non-authoritative answer:
google.com    canonical name = www.google.com.
www.google.com  canonical name = www.l.google.com.
www.l.google.com  canonical name = www.l.google.com.
www.l.google.com  internet address = 172.217.160.142

In this example, nslookup first shows the DNS server used. Then, it displays the canonical name (CNAME) records for google.com and www.google.com, which are both resolved to www.l.google.com. Finally, it shows the IP address of www.l.google.com.

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