Top 30 Networking Interview Questions and Answers [Includes All 3 Levels]

Are you preparing for a networking job interview and wondering what kind of questions you might face? Whether you’re a fresher entering the IT world or a seasoned professional aiming for a senior network engineer role, understanding core networking concepts is essential. 

This article brings you the top 30 networking interview questions and answers, carefully categorized into beginner, intermediate, and advanced levels. 

By the end, you’ll not only be better prepared for your next interview but also have a clearer grasp of how real-world networks function. So, without further ado, let us get started!

Beginner-Level Networking Interview Questions and Answers

If you’re just starting your career in networking or switching into IT from another field, these questions will help you build a strong foundation. 

They focus on basic concepts, terminology, and essential components that every network professional should understand. A solid grip on these topics is often enough to clear entry-level interviews with confidence.

1. What is a computer network?

A computer network is a collection of interconnected devices, such as computers, servers, routers, and switches, that share data and resources with each other. These networks enable communication through wired or wireless mediums. 

2. What is the difference between a hub, a switch, and a router?

These three devices are often used in networks but serve different purposes:

• Hub: A basic networking device that broadcasts data to all connected devices, regardless of the intended recipient. It works at the Physical layer (Layer 1) of the OSI model.
  
• Switch: Operates at the Data Link layer (Layer 2). It forwards data only to the specific device that needs it by using MAC addresses. More efficient than a hub.
  
• Router: Works at the Network layer (Layer 3). It connects different networks and routes data between them. It also assigns IP addresses and enables internet access.

3. What is an IP address?

An IP address (Internet Protocol address) is a unique identifier assigned to every device connected to a network. It enables devices to locate and communicate with each other.

There are two types of IP addresses: static (manually assigned) and dynamic (assigned via DHCP).

Read More: Components of the Internet: A Comprehensive Guide

4. What is a MAC address?

A MAC (Media Access Control) address is a unique hardware identifier assigned to a device’s network interface card (NIC). It is used within a local area network to ensure that data packets reach the correct physical device.

Example MAC address: 00:1A:2B:3C:4D:5E

Unlike IP addresses, MAC addresses are hardcoded and remain constant regardless of the network.

5. What is the OSI model?

The OSI (Open Systems Interconnection) model is a conceptual framework used to understand and design network systems. It divides networking into seven abstraction layers:

1. Physical – Hardware and cables
2. Data Link – MAC addressing and switching
3. Network – IP addressing and routing
4. Transport – Data transmission (TCP/UDP)
5. Session – Session control between devices
6. Presentation – Data formatting and encryption
7. Application – End-user services (e.g., HTTP, FTP)

Understanding the OSI model helps in troubleshooting and designing effective network solutions.

6. What are the types of networks?

Networks can be classified based on size, purpose, and geographical span:

• LAN (Local Area Network): Covers a small area like a home or office.
• WAN (Wide Area Network): Spans large distances; the Internet is the best example.
• MAN (Metropolitan Area Network): Covers a city or a campus.
• PAN (Personal Area Network): Short-range network, typically around a person (e.g., Bluetooth).

Each type of network serves a specific use case in both personal and enterprise environments.

7. What is DNS, and how does it work?

DNS (Domain Name System) acts as the Internet’s phonebook. It translates human-readable domain names (like example.com) into IP addresses that computers understand (like 93.184.216.34).

Here’s how it works:

1. You type a URL in your browser.
2. Your computer sends a DNS query to a DNS server.
3. The DNS server returns the corresponding IP address.
4. Your browser uses the IP to connect to the website’s server.

Without DNS, you’d have to remember IP addresses instead of domain names.

8. What is the difference between TCP and UDP?

Both TCP and UDP are transport layer protocols, but differ in functionality:

• TCP (Transmission Control Protocol): A Reliable, connection-oriented protocol. It ensures data is delivered in the correct order and without errors. Example: web browsing, email.
  
• UDP (User Datagram Protocol): Fast, connectionless protocol. It doesn’t guarantee delivery or order, but is useful for applications like video streaming or gaming where speed is crucial.

Think of TCP like a phone call and UDP like sending postcards.

9. What is subnetting?

Subnetting is the practice of dividing a large network into smaller, manageable sub-networks (subnets). This improves routing efficiency, network security, and resource utilization.

Example:

• An IP block like 192.168.1.0/24 can be split into two subnets:
  
  • 192.168.1.0/25 (0–127)
  • 192.168.1.128/25 (128–255)

Subnetting helps allocate IPs efficiently, especially in large organizations.

10. What is a firewall?

A firewall is a security system that monitors and filters incoming and outgoing network traffic based on predefined rules. It acts as a barrier between a trusted internal network and untrusted external networks (like the Internet).

Intermediate-Level Networking Interview Questions and Answers

Once you’re comfortable with the basics, it’s time to explore deeper concepts like subnetting, protocols, and traffic flow. 

These intermediate-level questions are common in interviews for roles like Network Support Engineer, System Administrator, or Junior Network Engineer. Let us see them one by one:

11. Explain the difference between IPv4 and IPv6.

IPv4 and IPv6 are versions of the Internet Protocol used to identify devices on a network.

• IPv4 (Internet Protocol version 4):
  
  • 32-bit address format
  • Example: 192.168.1.1
  • Provides around 4.3 billion unique addresses
  • Widely used but nearing exhaustion
    
• IPv6 (Internet Protocol version 6):
  
  • 128-bit address format
  • Example: 2001:0db8:85a3:0000:0000:8a2e:0370:7334
  • Provides virtually unlimited addresses (3.4×10³⁸)
  • Better efficiency, security, and scalability

IPv6 was introduced to address the limitations of IPv4 and to support the growing number of internet-connected devices.

12. What is NAT, and why is it used?

NAT (Network Address Translation) is a method used in routers to map private IP addresses to a single public IP address when accessing the internet.

Why it’s used:

• Conserves global IP address space
• Provides security by hiding internal IP addresses
• Enables multiple devices in a private network to share one public IP

13. What is DHCP, and how does it work?

DHCP (Dynamic Host Configuration Protocol) automatically assigns IP addresses and other network settings (e.g., gateway, DNS) to devices in a network.

How it works:

1. The device sends a DHCP Discover message.
2. The DHCP server responds with an Offer.
3. The device sends a Request to accept the offer.
4. The server sends an Acknowledgement.

This process simplifies IP management, especially in large networks where manually assigning addresses would be inefficient.

14. What is ARP?

ARP (Address Resolution Protocol) is used to map an IP address to its corresponding MAC address on a local network.

When a device wants to communicate with another on the same LAN, it:

1. Broadcasts an ARP request asking, “Who has IP 192.168.1.5?”
2. The device with that IP replies with its MAC address.
3. The original sender stores the mapping in its ARP table and sends the data.

ARP is essential for proper data delivery on Ethernet networks.

15. What is a default gateway?

A default gateway is a networking device (typically a router) that routes traffic from a local network to destinations outside that network.

If a device wants to send data to an IP address not in its subnet, it forwards the packet to the default gateway, which handles the routing.

16. What is a VLAN?

A VLAN (Virtual Local Area Network) is a logical segmentation of a physical network. Devices in the same VLAN can communicate with each other even if they’re not on the same physical switch.

17. What is port forwarding?

Port forwarding is a technique used to redirect network traffic from one IP/port combination to another. It allows external devices to access services inside a private network.

Example use case:
You host a web server on your internal IP 192.168.1.100 on port 80. By forwarding port 8080 from your public IP to this internal IP, anyone accessing yourdomain.com:8080 reaches your internal server.

18. Explain the TCP 3-way handshake.

The TCP 3-way handshake is the process used to establish a reliable connection between a client and server before data is exchanged.

1. SYN: Client sends a synchronization request to initiate communication.
2. SYN-ACK: Server acknowledges the request and replies with its synchronization.
3. ACK: Client acknowledges the server’s response.

Only after this handshake is complete can data be transmitted over a stable connection.

19. What is MTU, and how does it affect performance?

MTU (Maximum Transmission Unit) is the largest size (in bytes) of a packet that can be sent over a network interface.

• Standard Ethernet MTU is 1500 bytes
• If a packet exceeds the MTU, it may be fragmented or dropped

Impact on performance:

• Too small MTU = more packets = overhead
• Too large MTU = risk of fragmentation or dropped packets

Finding the optimal MTU size is key to achieving efficient and reliable network communication.

20. Coding: Write a Python script to check if a given IP is valid.

Here’s a simple Python script using the ipaddress module to validate IPv4/IPv6 addresses:

import ipaddress

def validate_ip(ip):

    try:

        ipaddress.ip_address(ip)

        return "Valid IP address"

    except ValueError:

        return "Invalid IP address"

# Example usage

print(validate_ip("192.168.0.1"))   # Output: Valid IP address

print(validate_ip("999.999.999.999"))  # Output: Invalid IP address

This function is often used in network configuration scripts or validation tools.

If you want to become a Network Engineer and don’t know where to start, read the blog – How to Become a Network Engineer? 6 Easy Steps to Get Started

Advanced-Level Networking Interview Questions and Answers

These questions are designed for experienced professionals who deal with enterprise-level networking, complex configurations, and security protocols. These answers require not just knowledge, but also clarity in explaining implementation.

21. How does BGP work?

BGP (Border Gateway Protocol) is a path vector routing protocol used to exchange routing information between autonomous systems (ASes) on the Internet.

How it works:

1. Routers exchange route advertisements with peers.
2. Routes are evaluated based on path attributes.
3. Best routes are added to the routing table and advertised to other peers.

BGP is crucial for global internet routing, making it a foundational concept in enterprise networking.

22. What is a Layer 3 switch?

A Layer 3 switch combines the functionality of a traditional switch (Layer 2) and a router (Layer 3).

• Switching (Layer 2): Forwards frames based on MAC addresses.
• Routing (Layer 3): Forwards packets based on IP addresses.

It’s typically used for inter-VLAN routing and advanced network segmentation.

23. What is the role of STP in networking?

STP (Spanning Tree Protocol) prevents network loops in Ethernet networks with redundant paths.

Why it needed?

• In a looped topology, frames can circulate indefinitely, causing broadcast storms.
• STP detects these loops and blocks some paths to form a loop-free tree structure.

Variants include RSTP (Rapid STP) and MSTP (Multiple STP) for faster convergence.

24. Explain the concept of QoS.

QoS (Quality of Service) is a set of techniques to prioritize certain types of traffic over others, ensuring performance for critical applications.

Example uses:

• Prioritizing VoIP traffic over file downloads
• Ensuring video conferences don’t lag even during high traffic

QoS is widely used in VoIP, streaming, gaming, and enterprise setups.

25. What is the difference between MPLS and VPN?

Both are used for secure and efficient networking, but differ in implementation:

MPLS is about performance and routing efficiency, while VPN is about secure tunneling.

Bonus: Scenario-Based Networking Questions and Answers

Scenario-based questions help interviewers evaluate how you analyze problems, make decisions under pressure, and implement network solutions in dynamic environments. Here are some of them below:

1. A user reports they can’t access the internet, but other users in the same office can. How would you approach this issue?

Answer: Start by checking the user’s physical connections and Wi-Fi status. If everything looks fine, try pinging the default gateway from the user’s machine. 

If that fails, the issue might be with the NIC or local IP settings. Run ipconfig (Windows) or ifconfig (Linux/Mac) to verify the IP configuration. 

Releasing and renewing the IP via DHCP (ipconfig /release and ipconfig /renew) often resolves such issues. Also, check for any MAC filtering or DHCP exhaustion on the router.

2. After changing a router, users report intermittent disconnections and slow access to internal resources. What could be the cause?

Answer: This might be due to incorrect routing table entries, MTU mismatches, or misconfigured NAT settings. Begin by verifying that the internal routes are correctly pointing to the new router. 

Use traceroute to identify where packets are getting delayed or dropped. Check logs for packet fragmentation or NAT translation errors. If multiple VLANs are in play, also confirm inter-VLAN routing settings.

3. Your organization’s website is accessible via IP address but not via domain name. What’s the likely problem?

Answer: This is a classic DNS issue. First, check if DNS resolution is working using nslookup yourdomain.com. If not, verify the DNS server settings on the client machines. 

Ensure that your public DNS records (A record, CNAME) are properly configured with your DNS provider. Internally, check for firewall rules or proxies blocking DNS requests. Restarting the local DNS resolver service or flushing the cache (ipconfig /flushdns) may also help.

4. You notice a broadcast storm affecting your LAN. What’s your immediate course of action?

Answer: A broadcast storm usually results from a Layer 2 loop. Immediately log into your switches and check for any loop-inducing connections. If STP (Spanning Tree Protocol) is not enabled, enable it to automatically block redundant paths. 

If STP is active, examine the topology using commands like show spanning-tree to identify and isolate the offending ports or devices. Physically disconnect suspected links if urgent mitigation is needed.

5. A remote office is complaining about high latency when accessing internal systems. How would you address the issue?

Answer: Start by testing latency and packet loss using tools like ping and traceroute. Review bandwidth utilization on both ends—the remote office and data center. 

Check for any congestion, misconfigured QoS policies, or routing inefficiencies. If the connection is over VPN, inspect tunnel configurations and ensure there’s no encryption overhead or MTU issues. If possible, use traffic shaping or prioritize critical applications using QoS to improve performance.

If you want to learn Networking that happens predominantly in Cloud Computing deeply through Azure, consider enrolling in GUVI’s Cloud Computing with Azure Course, which will arm you with the skills and knowledge to engage with the power of Microsoft Azure’s cloud services.

Conclusion

Networking is more than just cables and IP addresses—it’s the backbone of modern communication and infrastructure. From understanding the OSI model to configuring BGP or securing a wireless network, the depth of knowledge required can be broad. This guide has walked you through the most commonly asked interview questions across all levels, helping you build confidence and technical clarity. Keep practicing, stay curious, and remember: a strong grasp of networking fundamentals can set you apart in any tech interview.