Study of nslookup Command

 

Experiment

Study of nslookup Command

🎯 Aim

To query DNS servers and obtain domain name or IP address mapping using the nslookup command.

📘 Objective

By the end of this experiment, students will be able to:

  • Resolve domain names to IP addresses
  • Perform reverse DNS lookups
  • Query specific DNS servers
  • Understand DNS record types

📖 Theory

The nslookup (name server lookup) command is used to:

  • Query the Domain Name System (DNS)
  • Translate:
    • Domain name → IP address
    • IP address → Domain name

👉 It helps in:

  • Troubleshooting DNS issues
  • Verifying DNS configuration
  • Checking domain resolution

👉 It works in:

  • Non-interactive mode (single query)
  • Interactive mode (multiple queries)

🧾 Syntax

nslookup [options] <domain_or_ip> [dns_server]

🔧 Common Usage

Non-Interactive Mode:

nslookup google.com

Reverse Lookup:

nslookup 8.8.8.8

🧰 Prerequisites

  • Linux system
  • Internet connectivity
  • DNS configured

🔬 Procedure & Commands

1️⃣ Lookup Domain Name

nslookup google.com

2️⃣ Reverse DNS Lookup

nslookup 8.8.8.8

3️⃣ Use Specific DNS Server

nslookup google.com 8.8.8.8

4️⃣ Enter Interactive Mode

nslookup

Then use:

> google.com
> set type=mx
> google.com

5️⃣ Query Specific Record Types

  • MX Record (Mail Server): 
nslookup -type=mx google.com
  • NS Record (Name Server): 
nslookup -type=ns google.com
  • A Record: 
nslookup -type=a google.com

🖥️ Sample Output

Server:  8.8.8.8
Address: 8.8.8.8#53

Name:    google.com
Address: 142.250.183.14

🔍 Output Interpretation

FieldMeaning
Server        DNS server used
Address        IP of DNS server
Name        Domain name
Address (result)        Resolved IP

📝 Exercises for Students

  1. Resolve a domain name to IP address.
  2. Perform reverse lookup of an IP.
  3. Query MX records of a domain.
  4. Use different DNS servers and compare results.
  5. Explore interactive mode and run multiple queries.

❓ Viva Questions

  • What is DNS?
  • What is nslookup used for?
  • Difference between forward and reverse lookup?
  • What is an MX record?
  • Why use different DNS servers?

⚠️ Precautions

  • Results may vary depending on DNS server
  • Some domains may restrict certain records
  • Ensure correct syntax in interactive mode

✅ Result

The nslookup command is an essential tool for DNS querying and troubleshooting, helping users understand domain resolution and network configuration.

Comments

Post a Comment

Popular posts from this blog

Networks Lab PCCSL507 Semester 5 KTU CS 2024 Scheme - Dr Binu V P

 About Me   Dr Binu V P Syllabus Learn Linux well before you start- refer blog Experiments Familiarize Linux networking commands ifconfig ifplugstatus iftop ping ip traceroute mtr netstat whois nmap nmcli speedtest-cli bmon nslookup tcpdump Wireshark     Download Wireshark     Wireshark Documentaion     Setting up a capture     Capturing Live network data      Analysis of HTTP Protocol using Wireshark Socket Programming Basic Implementation of  TCP Client Server Communication using sockets. TCP Client-Server Communication to Identify Matrix Type (Upper/Lower/Diagonal) Implementation of UDP Client-Server Communication using Sockets in C UDP Client-Server Communication for Translating “New Generation English” to Formal English Cisco's Packet Tracer
Read more

Analysis of HTTP Protocol using Wireshark

Experiment Title Analysis of HTTP Protocol using Wireshark Aim To capture and analyze HTTP packets using Wireshark and study the structure of HTTP request and response messages. Objective To understand HTTP request and response formats To analyze packet-level communication using Wireshark To extract protocol-specific information from captured traffic Software Required Wireshark Web Browser (Chrome / Firefox / Edge) Internet Connection Theory 🌐 What is HTTP? HTTP (HyperText Transfer Protocol) is an application-layer protocol used for communication between web clients (browsers) and web servers. 🔁 HTTP Communication Client sends a GET request Server responds with: Status code Requested resource Metadata 📦 HTTP Message Types Request Message Contains: Method (GET, POST) URL Headers (Accept, User-Agent, etc.) Response Message Contains: Status code (200, 404, etc.) Headers (Content-Type, Content-Length, etc.) Body (HTML co...
Read more

Study and Use of ifconfig Command

   Experiment  Study and Use of ifconfig Command 🎯 Aim To familiarize students with the ifconfig command in Linux for viewing and configuring network interfaces. 📘 Objective By the end of this experiment, students will be able to: Display network interface details Enable/disable network interfaces Assign IP addresses manually Understand key networking parameters 🧰 Prerequisites Linux system (e.g., Ubuntu/Debian/Kali) Basic terminal knowledge Root or sudo privileges 📖 Theory The ifconfig ( interface configuration ) command is used to: View network interface configuration Assign IP addresses Enable or disable interfaces ⚠️ Note: On modern systems, ifconfig is deprecated and replaced by the ip command (from iproute2 ), but it is still widely used for learning and legacy systems. 🧾 Syntax ifconfig [interface] [options] interface → Network interface name (e.g., eth0 , wlan0 ) options → Actions like up, down, assigning...
Read more