Top Network Engineer Interview Questions for 2024

Beginner-level Interview Questions 

1. What is a network?

For instance, in a company, a LAN could be the network of computers in a single office, while a WAN could be the network connecting multiple offices in different cities. A network is a collection of interconnected devices that communicate with each other to share resources and information. Examples include local area networks (LANs) and wide area networks (WANs).

2. What is the OSI model? Describe its layers 

The OSI (Open Systems Interconnection) model is a conceptual framework used to understand network interactions in seven layers:

• Physical: Transmits raw data bits over a physical medium.
• Data Link: Provides node-to-node data transfer and handles error correction.
• Network: Manages routing and addressing (e.g., IP).
• Transport: Ensures reliable data transfer (e.g., TCP, UDP)
• Session: Manages sessions between applications.
• Presentation: Translates data formats and encrypts/decrypts.
• Application: Interfaces directly with user applications.

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

• Hub: A primary device broadcasts data to all connected devices; no intelligence.
• Switch: A more advanced device that directs data to specific devices based on MAC addresses.
• Router: Connects different networks, routes data between them, and manages traffic using IP addresses.

4. What is an IP address? 

An IP (Internet Protocol) address is a unique identifier for a device on a network used to send and receive data.

5. Explain the difference between IPv4 and IPv6 

• IPv4: Uses 32-bit addresses (e.g., 192.168.1.1), providing about 4.3 billion addresses.
• IPv6: Uses 128-bit addresses (e.g., 2001:0db8:85a3:0000:0000:8a2e:0370:7334), offering a vastly larger address space.

6. What is a subnet mask?

A subnet mask defines the range of IP addresses within a subnet, distinguishing the network portion from the host portion of an IP address.

7. What is a MAC address?

A MAC (Media Access Control) address is a unique identifier assigned to network interfaces for communication on the data link layer.

8. Explain the function of DNS.

DNS (Domain Name System) translates human-readable domain names (e.g., www.example.com) into IP addresses that computers use to identify each other.

9. What is DHCP?

DHCP (Dynamic Host Configuration Protocol) automatically assigns IP addresses and other network configuration parameters to devices on a network.

10. What is a VLAN?

VLAN (Virtual Local Area Network) segments a physical network into multiple logical networks, improving traffic management and security.

11. What are TCP and UDP?

• TCP (Transmission Control Protocol) is a connection-oriented protocol that ensures reliable data transmission through error checking and flow control.
• UDP (User Datagram Protocol) is a connectionless protocol that sends data without establishing a connection, offering lower latency but less reliability.

Read More: What are TCP and UDP, How Do They Work, and How Do They Compare?

12. What is a default gateway?

The default gateway (usually a router) forwards traffic from a local network to other networks or the Internet.

13. Explain the difference between static and dynamic IP addressing.

• Static IP: Manually assigned and does not change.
• Dynamic IP: Assigned by DHCP and can change periodically.

14. What is NAT (Network Address Translation)?

NAT translates private IP addresses to a public IP address, allowing multiple devices on a local network to share a single public IP address.

15. What is a firewall?

A firewall monitors and controls incoming and outgoing network traffic based on predetermined security rules.

16. What is a VPN (Virtual Private Network)?

A VPN creates a secure, encrypted connection over a less secure network, such as the Internet, to protect data and maintain privacy.

17. What is the purpose of a network protocol?

Network protocols define rules and conventions for communication between network devices, ensuring compatibility and effective data exchange.

18. Explain what ARP (Address Resolution Protocol) is.

ARP maps IP addresses to MAC addresses, enabling devices to communicate within a local network.

19. What is a proxy server?

A proxy server acts as an intermediary between clients and servers, often enhancing security, filtering content, or improving performance.

20. What is the difference between a public and a private IP address?

• Public IP: Routable over the Internet and unique across the globe.
• Private IP: Used within a private network and not routable over the Internet (e.g., 192.168.x.x).

21. What is SSID in wireless networking?

SSID (Service Set Identifier) is the name of a wireless network that allows devices to connect to it.

22. Explain what a traceroute does.

Traceroute is a network diagnostic tool that shows the path data takes from the source to the destination, listing each hop and its response time.

23. What is the purpose of the ping command?

The ping command tests the reachability of a host and measures the round-trip time for messages sent from the source to the destination.

24. What is a network topology?

Network topology refers to the physical or logical arrangement of devices and connections in a network, such as star, bus, or ring topologies.

25. What is the difference between half-duplex and full-duplex communication?

• Half-duplex: Data transmission occurs in one direction at a time.
• Full-duplex: Data transmission co-occurs in both directions.

Intermediate-Level Network Engineer Interview Questions

1. What is the difference between a layer two switch and a layer three switch?

• Layer 2 Switch: Operates at the data link layer, forwarding frames based on MAC addresses.
• Layer 3 Switch: Operates at the network layer, capable of routing packets based on IP addresses.

2. Explain what BGP (Border Gateway Protocol) is and how it works.

BGP is a path vector protocol that exchanges online routing information between autonomous systems (ASes). It uses path attributes to determine the best route.

3. What is EIGRP (Enhanced Interior Gateway Routing Protocol)?

EIGRP is a distance-vector routing protocol developed by Cisco that uses metrics such as bandwidth, delay, and load to determine the best path. 

4. What is OSPF (Open Shortest Path First)?

OSPF is a link-state routing protocol that uses the Dijkstra algorithm to find the shortest path within a single AS. It divides networks into areas to optimize routing.

5. What is MPLS (Multiprotocol Label Switching)?

MPLS is a technique that directs data from one network node to the next based on short path labels rather than long network addresses, improving speed and managing traffic.

6. Explain the Spanning Tree Protocol (STP).

STP prevents loops in network topologies by creating a loop-free logical topology. It dynamically turns off redundant paths and reactivates them if the active path fails.

7. What is a DMZ (Demilitarized Zone) in networking?

A DMZ is a network segment between an internal network and the Internet. It provides the Internet with an additional layer of security by isolating public-facing services from the internal network.

8. How does Quality of Service (QoS) work in a network?

QoS manages network traffic by prioritizing certain data types, ensuring that high-priority traffic, such as VoIP or video, receives the bandwidth it needs for optimal performance. Using networking commands is essential for setting up and monitoring QoS policies within a network to ensure optimal traffic management.

9. What are the differences between IPv6 and IPv4 addressing?

IPv6 provides a larger address space, improved header structure, and built-in security features compared to IPv4. It also simplifies address assignment and network configuration.

10. Explain what a VPN tunnel is.

A VPN tunnel is a secure, encrypted connection between two endpoints over a less secure network, providing privacy and data protection.

11. What is port forwarding?

Port forwarding redirects incoming traffic from one IP address and port to another. It is typically used to allow external access to services on a private network.

12. What is PAT (Port Address Translation)?

PAT, a type of NAT, maps multiple private IP addresses to a single public IP address but uses different port numbers to distinguish between sessions.

13. Explain the difference between the collision domain and the broadcast domain.

• Collision Domain: An area where data packets can collide, impacting network performance (e.g., in a hub-based network).
• Broadcast Domain: A network segment where all devices receive broadcast messages (e.g., in a VLAN).

14. What is a wildcard mask, and how is it used in networking?

A wildcard mask is used in access control lists (ACLs) to specify which bits in an IP address should be matched or ignored. It is used to define IP address ranges.

15. How does HSRP (Hot Standby Router Protocol) work?

HSRP provides redundancy for IP networks by configuring a virtual IP address shared between multiple routers. One router is active while others are on standby, ensuring network availability if the active router fails.

16. What is SNMP (Simple Network Management Protocol)?

SNMP is a protocol for managing and monitoring network devices such as routers, switches, and servers. It enables network administrators to collect performance data, configure settings, and receive alerts about network issues.

17. What is the difference between an access list and a firewall rule?

• Access List: A set of rules to control incoming and outgoing network traffic based on IP addresses, protocols, or ports. It is typically implemented on routers or switches.
• Firewall Rule: A broader term encompassing various security rules a firewall applies to filter traffic based on IP addresses, ports, protocols, and other criteria. Firewalls often provide more advanced features like stateful inspection and application-level filtering.

18. What is a route summarization?

Route summarization combines multiple IP address ranges into a single, more extensive address range, reducing the number of routes in a routing table and improving routing efficiency.

19. Explain what split-horizon is in routing.

Split-horizon is a technique used in distance-vector routing protocols to prevent routing loops by ensuring that routing information learned from one interface is not advertised back out of that same interface.

20. What is the purpose of VRRP (Virtual Router Redundancy Protocol)?

VRRP provides high availability for routing by creating a virtual router with a virtual IP address. Multiple physical routers can share this address, ensuring that if the primary router fails, one of the backup routers can seamlessly take over.

21. What are the different types of VPNs?

• Site-to-Site VPN: Connects entire networks over the Internet or a private network
• Remote Access VPN: Allows individual users to connect to a network remotely.
• Client-to-Site VPN: Similar to remote access, individual clients connect to a network via a VPN client.
• Intranet VPN: Connects multiple sites within a single organization
• Extranet VPN: Connects an organization's network with external networks, such as partners or clients.

22. How does Link Aggregation work?

Link Aggregation combines multiple physical network links into a single logical link to increase bandwidth and provide redundancy. This is often implemented using LACP (Link Aggregation Control Protocol) protocols.

23. What is VTP (VLAN Trunking Protocol)?

VTP is a Cisco proprietary protocol for managing VLAN configurations across multiple switches. It ensures VLAN consistency by propagating VLAN information to all switches within a VTP domain.

24. What is the purpose of network redundancy?

Network redundancy enhances reliability and availability by providing alternate paths or duplicate components to ensure continuous network service even if primary components fail.

25. How do you configure a static route on a Cisco router?

To configure a static route on a Cisco router, use the following command in global configuration mode:

ip route [destination_network] [subnet_mask] [next_hop_address or exit_interface] 

Example:

ip route 192.168.2.0 255.255.255.0 192.168.1.1 

Expert Level Network Engineer Interview Questions

1. Explain how to implement and troubleshoot BGP routing.

To implement BGP, configure BGP peers, specify autonomous system numbers and advertise networks. Troubleshoot BGP by checking peer status, route advertisements, and the BGP table. Commands like 'show ip BGP,' ‘show ip BGP summary,' and `debug ip bgp` are helpful.

2. What is the difference between BGP and OSPF?

• BGP is an inter-domain (external) routing protocol used between autonomous systems, focusing on policy-based routing and path selection.
• OSPF: An intra-domain (internal) routing protocol used within a single autonomous system, focusing on link-state information and the shortest path algorithm.

3. How do you secure BGP sessions?

Secure BGP sessions using techniques such as BGP MD5 authentication to ensure that BGP updates come from legitimate peers and apply prefix filtering to prevent the advertisement of incorrect routes.

4. What are the different types of BGP communities?

BGP communities are tags attached to routes to indicate special handling, such as:

• Standard Communities: Tags used for general route manipulation.
• Extended Communities: Include additional attributes like route targets and bandwidth constraints.

5. Explain the concepts of route reflection and confederations in BGP.

• Route reflection reduces the number of BGP sessions and controls routing information distribution within an AS by designating route reflectors that propagate routing updates.
• Confederations are a technique for splitting a large AS into smaller, more manageable sub-ASes while maintaining a single AS number for external communication.

6. How do you optimize OSPF areas?

Optimize OSPF areas by:

• Using appropriate area types (e.g., backbone area, stub area, not-so-stubby area) to manage routing information.
• Implementing summarization to reduce routing table size.
• Adjusting OSPF costs and metrics to influence path selection.

7. What are the best practices for configuring OSPF in a multi-area environment?

• Place the backbone area (Area 0) at the network's core.
• Use summarization to reduce the amount of routing information exchanged
• Designate appropriate ABRs (Area Border Routers) and ASBRs (Autonomous System Boundary Routers).

8. How do you implement MPLS in a network?

Implement MPLS by configuring MPLS on routers, defining Label Distribution Protocol (LDP) or Resource Reservation Protocol (RSVP) for label distribution, and setting up MPLS LSPs (Label Switched Paths) for data forwarding.

9. Explain the process of MPLS Traffic Engineering.

MPLS Traffic Engineering involves optimizing the distribution of network traffic across the network. It uses MPLS labels to establish explicit paths (LSPs) that can be optimized based on traffic patterns and network conditions, improving bandwidth utilization and reducing congestion.

10. What is a BGP route reflector, and why is it used?

A BGP route reflector is a router that redistributes BGP routes within an AS to reduce the number of required BGP peering sessions and simplify BGP configurations in large networks.

11. How does L2VPN and L3VPN work over MPLS?

• L2VPN: Extends Layer 2 networks over MPLS, allowing devices in different locations to communicate as if they were on the same local network.
• L3VPN: Provides Layer 3 connectivity over MPLS, creating virtual private routed networks that separate traffic between different customers.

12. What is SDN (Software-Defined Networking)?

SDN is an approach to network management that allows network administrators to manage network services through the abstraction of lower-level functionality. It separates the control plane from the data plane, enabling more flexible and programmable network management.

Read more: Network Engineer Job Description for 2024

13. How do you implement and manage SDN in an enterprise network?

Implement SDN by deploying SDN controllers and compatible switches. Manage SDN through APIs provided by the SDN controller, configure network policies, and use network virtualization to optimize traffic flows and resources.

14. Explain the concept of network function virtualization (NFV).

NFV involves virtualizing network functions such as firewalls, load balancers, and routers, allowing them to run on standard hardware instead of dedicated appliances. This enhances flexibility, scalability, and cost-efficiency.

15. What is VXLAN (Virtual Extensible LAN)?

VXLAN is a network virtualization technology that encapsulates Ethernet frames in UDP packets to extend Layer 2 networks over Layer 3 infrastructure, enabling scalable and isolated virtual networks.

16. How does EVPN (Ethernet VPN) work?

EVPN provides Ethernet services over an MPLS or VXLAN infrastructure. It uses BGP to distribute MAC address and IP information, enabling efficient multi-tenant network solutions and enhanced layer two and layer three connectivity.

17. Explain the purpose and function of network automation.

Network automation aims to streamline and simplify network management using scripts and tools to automate repetitive tasks, reduce manual errors, and increase operational efficiency.

18. How do you implement network security using ACLs and firewalls?

Implement network security by defining ACLs to filter traffic based on IP addresses, protocols, and ports, configuring firewalls to enforce security policies, and inspecting traffic for threats.

19. What is IPsec, and how is it used in VPNs?

IPsec (Internet Protocol Security) is a suite of protocols that secures IP communications by encrypting and authenticating packets. It is commonly used to establish secure VPN connections.

20. How do you handle multicast routing in an extensive network?

Handle multicast routing using protocols like PIM (Protocol Independent Multicast) to manage multicast group memberships and route multicast traffic efficiently.

Suggested Read: Top 10 Reasons to Learn Cybersecurity in 2024

21. Explain the concept of zero-trust network architecture.

Zero-trust network architecture assumes that threats could be internal or external and thus enforces strict access controls and verification for every user and device attempting to access resources.

22. How do you perform a network assessment and audit?

Perform a network assessment by evaluating network performance, security, and compliance through tools and methodologies such as network mapping, performance monitoring, vulnerability scanning, and policy reviews.

23. What are the key considerations for network capacity planning?

Key considerations include current and projected network traffic volumes.

24. How do you implement network monitoring and management tools? Implement network monitoring and management tools by:

• Choosing Tools: Select appropriate tools based on network size, complexity, and requirements (e.g., SNMP-based tools, network performance monitors).
• Deployment: Install and configure the tools on network devices and servers.
• Configuration: Set up monitoring parameters, thresholds, and alerts for critical metrics such as bandwidth usage, device status, and error rates.
• Integration: Integrate with other IT management systems for comprehensive visibility and control.
• Analysis: Use the tools to analyze network performance, detect issues, and generate reports for proactive management.

25. Explain the use of AI and machine learning in network management. 

AI and machine learning enhance network management by:

• Predictive Analytics: Forecasting network traffic patterns and potential issues using historical data.
• Anomaly Detection: Identifying unusual network behavior and security threats by analyzing patterns and deviations from normal behavior.
• Automation: Automating routine tasks such as configuration changes, network optimization, and fault management.
• Optimization: Optimizing network performance by dynamically adjusting resources and configurations based on real-time analysis.
• Self-Healing: Implementing self-healing mechanisms that automatically resolve network issues without human intervention.

Conclusion

Knowledge about networks and their engineering concepts and protocols forms a basis for creating and managing today's network architecture. So, to be versatile, whether you are a new engineer or an experienced one, it is essential to be aware of both the basic concepts and modern technologies to solve different networking problems. 

That is why preparing for the essential network solutions components of the examination, the more complex protocols like BGP and SDN, and other elements of the interview can help you demonstrate your knowledge in a complex network environment. To get a better understanding of these concepts and other cybersecurity techniques, you can join the Cyber Security Expert course from Simplilearn. This cybersecurity expert program will help you get ready for CEH, CompTIA Security+, and CISSP certifications, offering a holistic defense strategy against dynamic cyber threats. CEH emphasizes ethical hacking, CompTIA focuses on foundational security concepts, and CISSP covers advanced principles and management.