Cisco Nexus Interview Questions and Answers

Cisco Nexus switches are pivotal in modern data centers, and knowing how to manage and troubleshoot them is a key skill for network engineers.

Whether you're a beginner, an intermediate professional, or an expert, if you are looking for a job, you should prepare for various Cisco Nexus-related interview questions.

In this guide, we have provided a question bank containing the top 30 Cisco Nexus interview questions with their detailed answers. We have provided questions for freshers, intermediate, and experienced professionals. As a bonus for beginners, we have included situational interview questions.

Furthermore, you can also enroll in our Cisco Enterprise Training courses or Cisco Data Center training courses to get online training with real Cisco Devices.

Cisco Nexus Interview Questions For Beginners

These Cisco Nexus Basic questions cover the fundamentals of Cisco Nexus, including common theoretical knowledge about the Cisco Nexus switches. As a beginner, you should be well-read about the Cisco Nexus and know its details.

1. What is Cisco Nexus? 

Cisco Nexus is a series of switches designed for high-performance data center environments. They offer advanced features like low latency, scalability, and redundancy. These switches support both traditional and software-defined networking (SDN) and are optimized for virtualized environments. Cisco Nexus switches are often used to build large-scale, high-availability network infrastructures. 

2. What is the main difference between Cisco Nexus and Cisco Catalyst switches? 

Cisco Nexus switches are designed for data center environments, whereas Cisco Catalyst switches are typically used in enterprise campus networks. Nexus switches support more advanced features like virtual PortChannels, FCoE (Fibre Channel over Ethernet), and higher scalability. Catalyst switches focus more on access layer functionality and have more deployment in edge networks. Nexus switches are optimized for high-density, low-latency performance.

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3. Explain what VDC (Virtual Device Context) is in Cisco Nexus. 

A Virtual Device Context (VDC) is a logical separation within a physical Nexus switch that allows it to operate as multiple virtual switches. Each VDC has its own management plane, forwarding plane, and configuration. This feature is useful for network segmentation and allows for better resource utilization. VDC is typically used in large data centers to provide flexibility and reduce hardware requirements. 

4. What is the purpose of Nexus' FabricPath? 

FabricPath is a Cisco proprietary technology used to build scalable, efficient, and resilient Layer 2 networks in data centers. It operates using a network fabric and provides faster convergence than traditional spanning tree protocols. FabricPath uses a fabric-based architecture to eliminate issues like loops while providing flexibility and scalability. It is similar to Ethernet, but optimized for data center use cases. 

5. What is FCoE in Cisco Nexus? 

FCoE (Fibre Channel over Ethernet) is a technology that allows Fibre Channel frames to be transmitted over Ethernet networks. Cisco Nexus switches are capable of supporting FCoE to enable storage and data traffic to share the same network infrastructure. This reduces the need for separate Fibre Channel networks, simplifying the network architecture. FCoE is commonly used in data center environments for storage area network (SAN) integration. 

6. How does Nexus handle port-channel aggregation? 

Nexus switches support EtherChannel, which allows the aggregation of multiple physical interfaces into a single logical interface. This improves bandwidth and provides redundancy by load balancing traffic across multiple links. Nexus supports various protocols like PAgP (Port Aggregation Protocol) and LACP (Link Aggregation Control Protocol) for creating port channels. EtherChannel helps in enhancing network resilience and availability. 

7. What is NX-OS? 

NX-OS (Nexus Operating System) is the operating system running on Cisco Nexus switches. It is designed for data center environments and provides high availability, scalability, and advanced network virtualization features. NX-OS offers a command-line interface (CLI) similar to Cisco’s IOS, but with enhanced capabilities such as support for SAN, storage networking, and virtualization. NX-OS is optimized for managing large-scale data center infrastructures. 

8. What is the use of Layer 2 and Layer 3 switching in Nexus? 

Cisco Nexus switches support both Layer 2 (data link layer) and Layer 3 (network layer) switching. Layer 2 switching handles MAC address forwarding and is used for VLANs and bridging. Layer 3 switching allows IP routing, providing inter-VLAN routing and enabling communication between different subnets. Nexus supports advanced features like routing protocols, VXLAN, and MPLS. 

9. What is a Spanning Tree Protocol (STP), and how does it work on Nexus? 

Spanning Tree Protocol (STP) is used to prevent network loops in Layer 2 networks by designating a root switch and blocking redundant paths. Cisco Nexus switches support RSTP (Rapid Spanning Tree Protocol) and PVST+ (Per VLAN Spanning Tree Plus). STP ensures that there is only one active path for data transmission while blocking others to prevent loops. Nexus switches provide faster convergence times for STP compared to traditional implementations. 

10. What is the role of QoS (Quality of Service) in Nexus switches? 

Quality of Service (QoS) in Cisco Nexus switches is used to manage network traffic and prioritize critical applications or services. QoS ensures that high-priority traffic, such as voice or video, gets the bandwidth it needs, while lower-priority traffic is deprioritized. Nexus supports QoS policies that allow fine-grained control over traffic behavior based on criteria like IP address, application type, and protocol. This ensures better overall network performance and resource allocation. 

Cisco Nexus Interview Questions For Intermediate

The following are some of the intermediate-level interview questions that one can expect during a Cisco Nexus interview 

11. What is VXLAN, and how does it work on Nexus switches? 

VXLAN (Virtual Extensible LAN) is a technology that encapsulates Layer 2 Ethernet frames into Layer 3 UDP packets, enabling the creation of virtual networks over a physical Layer 3 infrastructure. Nexus switches support VXLAN for network virtualization and to extend VLANs across data centers. VXLAN helps overcome the 4,096 VLAN limit by using a 24-bit VXLAN Network Identifier (VNI). It’s commonly used in multi-tenant data centers and SDN environments for scalability and flexibility. 

12. Explain the concept of virtual port channels (vPC). 

Virtual Port Channel (vPC) is a Cisco technology that allows a single logical link between two physical switches. It helps in avoiding the blocking of links that traditional STP would create, providing increased bandwidth and redundancy. With vPC, you can connect a device to two Nexus switches simultaneously without causing a loop, improving fault tolerance. vPC also helps in simplifying network configurations by allowing more flexibility in deploying network topologies. 

13. What is the difference between OSPF and EIGRP on Nexus switches? 

OSPF (Open Shortest Path First) is an open standard, link-state routing protocol, while EIGRP (Enhanced Interior Gateway Routing Protocol) is a Cisco proprietary, hybrid routing protocol. OSPF uses the Dijkstra algorithm and is commonly used in multi-vendor environments, while EIGRP is faster to converge and uses a distance-vector algorithm. Both are supported on Nexus switches, but OSPF is preferred for larger, more diverse networks, whereas EIGRP is used for faster, more scalable Cisco-specific environments. 

14. What are the key benefits of using OTV (Overlay Transport Virtualization) in Cisco Nexus? 

Overlay Transport Virtualization (OTV) allows data centers to extend Layer 2 connectivity across multiple geographically dispersed sites over Layer 3. It provides a simple and efficient method to extend VLANs and manage traffic between data centers without the complexity of traditional technologies. OTV helps in disaster recovery and load balancing by enabling seamless traffic migration between sites. It also reduces the need for complex routing protocols to maintain Layer 2 communication over long distances. 

15. How does NX-OS handle troubleshooting and diagnostics? 

NX-OS provides several commands for troubleshooting, including `show` and `debug` commands to monitor various aspects of the switch. It includes tools like `show system internal` for detailed logs and `show tech-support` for comprehensive diagnostics. Cisco Nexus also supports Syslog for external logging and SNMP for monitoring. Additionally, commands like `ping`, `traceroute`, and `diagnose` help in identifying network issues. 

16. What is the purpose of the Fabric Extender (FEX) in Nexus architecture? 

A Fabric Extender (FEX) is a Cisco technology that allows remote switches to connect to a parent Nexus switch, acting as a downstream extension of the Nexus fabric. FEX provides a way to scale out the network without adding additional Layer 3 switches. The parent switch manages the FEX and handles all data forwarding, reducing the complexity of the network architecture. This setup is useful in large data centers and helps in simplifying network topology while ensuring scalability. 

17. Explain the role of the Control Plane in Nexus. 

The control plane in Nexus handles the exchange of routing and forwarding information between devices, including Layer 3 routing protocols like OSPF and EIGRP. It is responsible for creating and maintaining the routing tables and managing MAC address tables. In Nexus switches, the control plane is separated from the data plane for better performance and security. Nexus uses the Virtual Supervisor Module (VSM) in a virtualized environment to manage control plane functions. 

18. How is network virtualization handled in Nexus switches? 

Nexus switches support network virtualization technologies like VRF (Virtual Routing and Forwarding) and VLANs. VRF allows the segmentation of routing tables, providing multiple virtual networks within a single physical device. Nexus switches can also implement VXLAN for Layer 2 over Layer 3 networks, allowing for large-scale virtual networks. These features help in isolating traffic, improving security, and simplifying network management in multi-tenant environments. 

19. What is the role of MPLS in Nexus? 

MPLS (Multi Protocol Label Switching) in Nexus switches is used for efficient packet forwarding across Layer 3 networks. It allows for the creation of label-switched paths (LSPs), improving network scalability, traffic engineering, and fault tolerance. MPLS in Nexus helps in connecting geographically dispersed sites with consistent performance and reliability. It is commonly used in large enterprises and service provider environments for wide-area network (WAN) optimization. 

20. What is the purpose of the Nexus 7000 series supervisor module? 

The Nexus 7000 series supervisor module is the brain of the Nexus 7000 chassis, providing centralized management and control over the entire system. It handles tasks like route processing, Layer 2 and Layer 3 forwarding, and policy enforcement. The supervisor module also supports high-availability configurations, ensuring minimal downtime. It integrates with the Nexus' high-density I/O modules to ensure efficient data flow and scalability. 

Cisco Nexus Interview Questions For Experienced 

The following are some commonly asked advanced Cisco Nexus Interview questions that one can expect during a Cisco Nexus interview. 

21. Can you explain the architecture of Cisco Nexus 9000 series switches? 

The Cisco Nexus 9000 series switches are designed with both traditional and software-defined data center architectures in mind. They offer a range of models, including fixed and modular configurations, that can run both NX-OS and ACI (Application Centric Infrastructure). The Nexus 9000 series provides high scalability, high-performance throughput, and support for modern workloads like cloud and virtualized environments. They also integrate with automation and orchestration tools, enabling advanced network programmability and SDN capabilities. 

22. How does Cisco’s Application Centric Infrastructure (ACI) integrate with Nexus 9000 switches? 

Cisco ACI is an SDN solution that integrates directly with Nexus 9000 switches to provide a policy-driven approach to networking. ACI uses the Nexus 9000 as a hardware platform, leveraging its programmability to dynamically allocate network resources based on application needs. The solution allows for centralized network management and automation using the APIC (Application Policy Infrastructure Controller). ACI simplifies network operations, enhances scalability, and improves security by enabling application-aware networking. 

23. What is Cisco’s NDFC (Network Data Center Fabric Controller), and how does it work with Nexus? 

Cisco NDFC (Network Data Center Fabric Controller) is a software solution that provides centralized management for data center networks. It works with Nexus switches to automate the deployment and management of network fabrics, both underlay and overlay. NDFC allows for rapid provisioning of network services and simplifies network monitoring and troubleshooting. It integrates with ACI, SDN controllers, and other Cisco data center solutions for an automated, highly available infrastructure. 

24. Explain how the “Nexus 9000” integrates with EVPN (Ethernet VPN). 

EVPN (Ethernet VPN) is a control-plane technology used for scalable Layer 2 and Layer 3 virtualized networks. Nexus 9000 switches support EVPN for VXLAN, enabling better scalability, efficiency, and automation. EVPN enables the extension of Layer 2 networks over Layer 3 infrastructure, providing flexibility and simplifying multi-tenant data center designs. It enhances the management of routing and switching, improving redundancy and eliminating limitations of traditional STP-based designs. 

25. What are some key differences between ACI mode and NX-OS mode on Nexus 9000? 

In ACI mode, Nexus 9000 switches operate as part of an SDN architecture with centralized policy control via the APIC (Application Policy Infrastructure Controller). This mode emphasizes automation, scalability, and policy-driven network provisioning. In contrast, NX-OS mode is more traditional, providing a network-centric model with a focus on manual configuration, VLANs, and routing protocols. The choice between the two modes depends on the organization’s requirements for programmability and automation. 

26. How does Cisco Nexus handle BGP EVPN for Layer 2 over Layer 3 networks? 

BGP EVPN (Ethernet VPN) is a control-plane solution that enables Layer 2 and Layer 3 services over a Layer 3 network. In Nexus switches, BGP EVPN facilitates the extension of Layer 2 networks across geographically dispersed sites while eliminating the need for traditional spanning tree protocols. It improves scalability, flexibility, and redundancy in data center networks. BGP EVPN supports advanced features such as MAC address learning and multi-tenancy, making it ideal for large-scale deployments. 

27. What is Cisco’s Nexus 1000V, and how does it integrate with VMware vSphere? 

The Nexus 1000V is a virtual switch designed for VMware vSphere environments, enabling Layer 2 switching and advanced networking features within virtualized environments. It integrates with VMware vCenter to provide network visibility and management for virtual machines. The Nexus 1000V extends network policies to virtual machines, allowing network admins to control traffic in the virtualized layer. This solution enhances network security and simplifies VM mobility in cloud environments. 

28. What is the purpose of the ACI fabric in Cisco Nexus architecture? 

The ACI fabric is an integral part of Cisco’s Application Centric Infrastructure (ACI) and is used to connect various components of the data center, including servers, storage, and networking equipment. In Nexus environments, the ACI fabric simplifies data center management by centralizing policy enforcement and automation. The fabric uses a spine-leaf architecture to ensure high performance, scalability, and fault tolerance. ACI fabric automates provisioning, optimizes traffic, and improves operational efficiency. 

29. Explain how Cisco Nexus achieves high availability and redundancy. 

Cisco Nexus switches use several redundancy mechanisms to ensure high availability. These include hot-swappable components, dual supervisor modules, and power supplies for non-disruptive upgrades and minimal downtime. In a multi-chassis environment, technologies like vPC (Virtual Port Channel) and FEX (Fabric Extender) provide link and device redundancy, preventing single points of failure. In addition, features like HSRP, VRRP, and GLBP provide router redundancy and ensure seamless failover for Layer 3 operations. 

30. How do you configure VXLAN with a Nexus 7000 or Nexus 9000 switch? 

To configure VXLAN on a Nexus switch, you first need to configure the underlay network (IP routing). Then, create a VXLAN Network Identifier (VNI) for each VXLAN segment, which maps to an existing VLAN or subnet. Configuration involves enabling VXLAN encapsulation, creating a bridge domain, and associating VNIs with VLANs. Additionally, you configure the Layer 3 VXLAN control-plane, such as BGP EVPN, to handle MAC address learning and multi-destination traffic forwarding. 

Experience-Based Cisco Nexus Interview Questions 

Experience-based interview questions for roles involving Cisco Nexus or similar technologies typically assess not just your technical expertise but also your problem-solving skills, communication, teamwork, and ability to handle challenging situations.

Here are examples of such questions and tips on how to approach them:  

31. Tell me about a time you resolved a complex network issue involving Cisco Nexus devices. 

I encountered a situation where a misconfigured vPC on Nexus 9000 switches caused intermittent connectivity issues in a production environment. I analyzed logs and ran show tech-support vpc to identify the root cause—a VLAN mismatch. After correcting the configuration and performing validation tests, the issue was resolved with minimal downtime. I then updated our documentation and trained the team to prevent future occurrences. This improved both team knowledge and operational stability.

32. Describe a time you had to learn a new Nexus feature or technology to complete a project. 

"While implementing VXLAN on Nexus 9300s, I realized I needed deeper knowledge of EVPN to meet the project’s goals. I quickly enrolled in Cisco’s EVPN training, studied official documentation, and practiced in a lab. Applying what I learned, I successfully configured the environment, enabling dynamic traffic routing across data centers. The client praised the seamless delivery of the solution. This experience underscored the importance of adaptability and continuous learning." 

33. Can you provide an example of a situation where you had to troubleshoot under pressure? 

"During a critical financial transaction period, network latency spiked unexpectedly on a Nexus 7000-based infrastructure. I immediately gathered metrics using the show processes cpu history and pinpointed a CPU-hogging process caused by a misconfigured QoS policy. I corrected the policy during a scheduled window and implemented traffic monitoring. The issue was resolved before impacting business operations. My quick response maintained client confidence and ensured minimal disruption." 

34. How do you ensure successful communication when working with cross-functional teams? 

"In a project involving Nexus device upgrades, I ensured communication by organizing regular meetings and using collaboration tools like Slack for real-time updates. I documented technical requirements in clear, non-technical language for stakeholders from different teams. I also made sure to address concerns promptly and adapt timelines as needed. This approach kept everyone informed and aligned, leading to a smooth deployment. Clear and open communication was key to the project's success." 

35. Tell me about a time you implemented automation with Cisco Nexus devices. 

"I was tasked with standardizing configurations across dozens of Nexus 9000 switches. Using Ansible, I wrote playbooks to automate VLAN and port configurations, significantly reducing manual effort. I tested the scripts in a sandbox environment before applying them to production. The automation saved 50% of configuration time and minimized human errors. It also became a foundation for ongoing network operations automation." 

36. Describe a challenging decision you made regarding network security on Nexus devices. 

"During a compliance audit, we discovered unused ports on Nexus 7000 switches, posing a potential security risk. I recommended disabling or shutting down all unused ports while implementing port-based authentication. Although this added complexity, it was critical for securing the network. I coordinated with application owners to avoid disruptions and documented the changes for compliance records. The decision reinforced our network's security posture." 

37. How do you prioritize tasks during a major network upgrade? 

"In a Nexus infrastructure upgrade, I prioritized tasks by assessing their impact on uptime and aligning them with the business’s operational windows. I created a detailed schedule, first testing in a lab and addressing high-risk tasks like firmware updates early. I communicated the plan with all stakeholders and included contingencies for potential delays. By tackling the highest-priority tasks first, the upgrade completed on time without service disruptions. Effective planning ensured success." 

38. Share an experience where you optimized network performance using Cisco Nexus. 

"During a performance review, I identified suboptimal traffic flow caused by redundant paths in the Nexus 9000 topology. I reconfigured vPC settings and introduced FabricPath to optimize load distribution. After implementing the changes, I monitored performance metrics, which showed a 30% improvement in throughput. The optimized configuration enhanced both application performance and user experience. This demonstrated my ability to identify and resolve inefficiencies." 

39. How do you handle conflicting opinions when collaborating on network designs? 

"In designing a Nexus-based data center, the team disagreed on using VXLAN versus traditional VLANs. I facilitated a meeting to present a comparative analysis of both options, including scalability and cost. By addressing each stakeholder's concerns and focusing on the project’s long-term goals, we reached a consensus on using VXLAN. This collaborative approach ensured buy-in from all team members. The solution proved scalable and effective." 

40. Give an example of a time when you proactively improved a network process. 

"I noticed that manual firmware updates on Nexus switches were causing inconsistencies and delays. To address this, I created a step-by-step standard operating procedure (SOP) and implemented an automated upgrade process using Python scripts and API integration. The automation reduced update times by 40% and ensured uniformity across devices. I also trained the team to use the new process, further enhancing efficiency. This proactive effort streamlined operations and improved reliability." 

Conclusion 

Preparing for a Cisco Nexus interview requires a solid understanding of both the hardware and software aspects of Nexus switches, as well as their integration into modern data center environments.

Whether you're just starting in networking or you're an experienced engineer, mastering concepts like NX-OS, vPC, VXLAN, ACI, and FabricPath will set you up for success.

Interview questions span from basic network functionality to advanced features like BGP, EVPN, and SDN integrations, reflecting the broad capabilities of Nexus switches in supporting scalable, reliable, and efficient data center operations.

By understanding these technologies and their use cases, you can confidently navigate a wide range of interview scenarios and demonstrate your proficiency in managing and troubleshooting Cisco Nexus environments.