Top 30 Computer Network Engineer Interview Questions and Answers [Updated 2025]

To calculate the number of hosts in a subnet with a subnet mask of 255.255.255.0, I convert the mask to binary which is 11111111.11111111.11111111.00000000. There are 8 bits set to zero. Using the formula, I calculate 2^8 - 2 = 254 usable hosts.

A hub is a basic networking device that simply forwards data to all ports. A switch is more intelligent; it sends data only to the device that needs it by using MAC addresses. A router connects different networks and routes data between them using IP addresses. Use a hub in small, simple networks, a switch for larger local networks, and a router for connecting to the internet.

TCP (Transmission Control Protocol) is a connection-oriented protocol that ensures reliable data transmission through error checking and retransmission, making it suitable for applications like web browsing. UDP (User Datagram Protocol), on the other hand, is connectionless and does not guarantee delivery, which makes it ideal for real-time applications like online gaming or video conferencing where speed is crucial and a few lost packets are acceptable.

First, I would ask users for specifics about when and where they experience connectivity issues. Then, I would analyze if there's a pattern and use monitoring tools to check for anomalies during those times.

I primarily use SolarWinds and Wireshark. SolarWinds helps me monitor network performance through dashboards that show latency and traffic, while Wireshark allows for deep packet analysis. I assess health by checking for packet loss and response times, and I once identified a bottleneck using Wireshark that improved our overall bandwidth.

When configuring a firewall, it's essential to start with a clear security policy that outlines what traffic should be allowed or blocked. Additionally, segmenting your internal networks will reduce the risk of lateral movement in case of a breach.

The 2.4 GHz frequency has a longer range and better penetration through walls, making it suitable for larger areas. However, it's more prone to interference. The 5 GHz frequency offers faster speeds and less congestion but has a shorter range. It's ideal for high-bandwidth activities in smaller spaces.

Quality of Service (QoS) is a set of techniques to manage network resources and ensure the performance of high-priority applications. It is important because it helps ensure that latency-sensitive data, like VoIP calls, receive the necessary bandwidth and minimal delay. To implement QoS, I use methods like traffic classification and prioritization, often utilizing protocols such as DiffServ to differentiate between different types of traffic. For instance, I can configure router settings to prioritize voice traffic over regular web browsing traffic.

A VPN, or Virtual Private Network, creates a secure tunnel between a user's device and a corporate network over the internet. It encrypts the data sent through this tunnel, which protects sensitive information from eavesdropping. Common protocols include IPSec and SSL/TLS. The main benefits are enhanced security, remote access for employees, and safeguarding company data from cyber threats.

There are five main types of network topologies: star, ring, bus, mesh, and tree. The star topology's biggest advantage is that it's easy to install and manage, but if the central hub fails, the whole network goes down. The ring topology allows for a simple setup and data travels fast, but if one connection breaks, the entire network can be disrupted.

In my previous role, we moved from IPv4 to IPv6. I took a course to understand the differences and implications. I updated our network configuration accordingly and conducted training sessions for my team. This ensured a smooth transition and improved our network security.

During a critical client meeting, I noticed the network was down. I quickly checked the network status on our monitoring tool, which indicated a router failure. I physically accessed the router and noticed a power issue. After fixing the power connection, I tested the connectivity, and the network was restored. I then implemented a UPS for the router to avoid future outages.

In a project to optimize our company's WAN, I collaborated with a team of network engineers. My role was to analyze the current performance metrics and identify bottlenecks. We implemented QoS policies and upgraded our routing protocols. As a result, we improved network speed by 30% over two months.

In a project at my last job, I disagreed with a colleague on whether to use static IPs or DHCP for a new subnet. We had a meeting to discuss each approach's pros and cons. I presented the benefits of DHCP for easier management, while he highlighted the control of static IPs. After discussion, we decided on a hybrid approach that satisfied both sides, and we learned a lot about compromise.

In a project with a small business, I explained a network outage caused by router failure. I likened the router to a traffic light managing data flow. I broke down the issue into how data travels and assured them the problem would be fixed quickly. I summarized by stating the actions we were taking and asked if they needed further clarification.

In my previous role, I worked on upgrading our corporate network within a week due to a sudden change in policy. I prioritized tasks by identifying critical components and coordinated with my team to tackle those. Regular check-ins kept us aligned, and we faced challenges with delays in equipment delivery, which I resolved by sourcing alternative suppliers quickly. We completed the project on time, enhancing network performance significantly.

In my last position, I noticed that our network was experiencing sporadic slowdowns. To address this, I implemented a network monitoring tool to analyze traffic patterns. By proactively checking for bottlenecks and adjusting our bandwidth allocation accordingly, we were able to reduce user complaints by 30% over the next quarter.

In my previous role, I led a project to upgrade our network infrastructure to support remote work. I coordinated a team to assess existing bottlenecks and implemented a new routing protocol, which improved our network speed by 50%. The successful completion of this project resulted in a smoother experience for our remote employees.

I stay updated by following prominent blogs like Packet Pushers and attending webinars. Recently, learning about SD-WAN through a webinar allowed me to recommend it to my manager, leading to a successful deployment that improved our network performance.

At my last job, I noticed our network latency was affecting application performance. I conducted a review of our routing protocols and identified inefficient paths. I implemented OSPF to optimize our routing, which reduced latency by 30% and improved user satisfaction. I collaborated with the team to ensure a smooth transition.

First, I would identify the source of the unauthorized access by checking network logs. Then, I would isolate the affected systems from the network to prevent any further compromise. I would also notify the security team while informing relevant stakeholders about the incident. After that, I would analyze the logs to understand how the breach occurred and identify any vulnerabilities. Finally, I would implement necessary measures based on the findings to prevent future incidents.

First, I would evaluate the current network capacity and identify any bottlenecks. Then, I would calculate the expected bandwidth and device requirements for 200 new employees, ensuring we have enough access points and switches to support them. I would also design the network with redundancy in mind to prevent downtime.

First, I would identify which services are impacted and inform the team. Then, I would check the device logs and status indicators for issues. If needed, I would implement a temporary solution until the device can be repaired or replaced.

I would start by reviewing our current network expenses to pinpoint the highest costs. Then, I would evaluate our vendor contracts for opportunities to renegotiate terms or switch to more cost-effective providers. Implementing software-defined networking could also help streamline our operations.

I would first evaluate the existing network to pinpoint areas in need of the upgrade. Then, I'd develop a comprehensive timeline outlining each phase of the upgrade. I would inform all stakeholders about the schedule and potential downtime. Next, I'd run a pilot test to ensure the upgrade works smoothly before the full rollout. Finally, I’d aim to execute the upgrade during off-peak hours to minimize disruptions.

I would first look at the vendor's reputation by researching reviews and feedback from current users. Then, I would analyze the total cost of ownership including initial purchase, maintenance, and potential upgrade costs. It's also important to ensure the equipment is compatible with our current network infrastructure, and I would check the support options they offer, including warranty terms. Finally, I would evaluate how scalable their solutions are for future growth.

I would first clarify the exact changes being requested and then outline my security concerns by explaining the potential risks. I would suggest alternatives that enhance security while still addressing the department's needs.

I foresee compatibility issues as legacy systems might not support modern network protocols. To address this, I would implement middleware solutions that can translate between old and new protocols while ensuring that performance is not affected.

First, I would review the new regulations to understand their requirements. Then, I'd audit our existing network protocols to identify any gaps. Based on that, I'd create a compliance plan detailing the necessary changes and schedule for implementation.

I would implement a comprehensive disaster recovery plan that includes redundant network paths and ensure that we have diverse routing protocols in place. Regular backups of all configurations and data are essential, and I would advocate for a secondary site or cloud solution to ensure seamless business continuity.