Top 30 Most Common Cn Interview Questions You Should Prepare For
Written by
James Miller, Career Coach
Preparing for a technical interview, especially in specialized fields like network engineering, requires more than just theoretical knowledge. Interviewers want to gauge your practical skills, problem-solving abilities, and experience with specific technologies. For roles involving Cisco networking equipment, mastering key concepts and being able to articulate your experience is paramount. This guide delves into 30 of the most frequently asked cn interview questions, offering insights into why they are asked and how to structure your responses effectively. By reviewing these common cn interview questions and preparing thoughtful answers, you can significantly boost your confidence and performance in your next interview. Navigating these typical cn interview questions will set you apart.
What Are cn interview questions?
cn interview questions, in the context of network engineering, specifically refer to interview questions designed to assess a candidate's knowledge and practical skills related to Cisco networking products and technologies. Cisco is a dominant player in the networking industry, and many network roles require proficiency with their routers, switches, firewalls, and associated software like Cisco IOS, NX-OS, and platforms like Cisco DNA Center. These questions cover a broad range of topics, from fundamental network concepts (like routing, switching, security, and troubleshooting) as applied to Cisco devices, to more advanced topics such as SD-WAN, automation, and specific Cisco features (like EIGRP, HSRP, VTP). Preparing for these cn interview questions is essential for anyone pursuing a network engineering career focused on Cisco infrastructure. Mastering common cn interview questions is a key step.
Why Do Interviewers Ask cn interview questions?
Interviewers ask cn interview questions for several crucial reasons. Firstly, they need to verify a candidate's hands-on experience and technical depth with the specific equipment and software they will be expected to work with daily. Since Cisco is so prevalent, demonstrated competence with Cisco IOS commands, configuration syntax, and troubleshooting procedures is often a baseline requirement. Secondly, these questions help assess a candidate's problem-solving methodology. Troubleshooting cn interview questions or scenario-based queries reveal how a candidate approaches complex network issues. Thirdly, they evaluate understanding of core networking principles through the lens of Cisco implementation. Finally, cn interview questions involving advanced topics like automation or SDN indicate a candidate's willingness to adapt to evolving network technologies and their potential to contribute to modern network architectures. Proficiency with cn interview questions is highly valued.
Preview List
Can you describe your experience with Cisco networking equipment and software?
What steps do you follow to configure a new Cisco router or switch?
How do you troubleshoot a network connectivity issue?
Can you explain the differences between OSPF, EIGRP, and BGP routing protocols?
How do you ensure network security in a Cisco-based environment?
What is the purpose of VLANs and how do you configure them on a Cisco switch?
What is an Access Control List (ACL) and how do you apply it?
Describe your experience with Cisco IOS and other Cisco operating systems.
How do you monitor network performance in Cisco environments?
Can you explain the function of Spanning Tree Protocol (STP)?
How do you configure Quality of Service (QoS) on Cisco devices?
What is NAT and how does it work?
How would you secure a wireless network?
What is HSRP and how does it provide redundancy?
Explain how to set up a site-to-site VPN on Cisco routers.
What are the differences between TCP and UDP? When would you use each?
How do you troubleshoot a slow network connection?
How do you recover from a network outage?
What is DHCP relay and when is it useful?
What causes packet loss and how do you troubleshoot it?
How do you stay updated on networking trends?
What is Software-Defined Networking (SDN)?
Describe a complex network solution you implemented and challenges faced.
How do you handle network redundancy and failover configurations?
What tools do you use for automating Cisco network tasks?
Explain BGP basics and how you set up BGP?
What is the function of the
show interfacecommand?What challenges exist when integrating legacy systems with modern networks?
How do you ensure compliance with industry standards and regulations?
How do you configure VLAN trunking on Cisco switches?
1. Can you describe your experience with Cisco networking equipment and software?
Why you might get asked this:
To gauge your practical, hands-on familiarity with Cisco hardware and software, assessing if your experience aligns with the role's requirements.
How to answer:
Be specific about the types of devices (routers, switches, firewalls), operating systems (IOS, NX-OS), and tools you've used, highlighting key projects.
Example answer:
I have 5 years experience configuring Cisco Catalyst/Nexus switches, ISR routers, and ASA firewalls. I'm proficient in IOS/NX-OS CLI, implementing OSPF/BGP routing, VLANs, ACLs, and managing devices with Cisco Prime.
2. What steps do you follow to configure a new Cisco router or switch?
Why you might get asked this:
To assess your systematic approach to device setup, ensuring you cover essential configurations like initial access, IP addressing, and basic security.
How to answer:
Outline a logical sequence: console access, basic settings, interface config, routing, security, verification, and saving.
Example answer:
Connect via console, enter global config mode, set hostname, configure management interface/VTY lines (SSH), define interface IPs, configure routing, save config, and verify connectivity.
3. How do you troubleshoot a network connectivity issue?
Why you might get asked this:
To evaluate your problem-solving methodology. A structured approach demonstrates efficiency and understanding of network layers.
How to answer:
Describe a layered or systematic method (e.g., OSI model): check physical, interface status, IP config, routing, firewall/ACLs, use diagnostic tools.
Example answer:
I start by verifying physical connections, checking interface status and errors, then IP configurations. I use ping/traceroute to isolate the fault domain, review logs, and check ACLs or firewall rules.
4. Can you explain the differences between OSPF, EIGRP, and BGP routing protocols?
Why you might get asked this:
Tests fundamental routing protocol knowledge, crucial for designing and managing complex networks within and between autonomous systems.
How to answer:
Explain the core type (link-state, hybrid, path-vector), primary use case (intra-AS, inter-AS), and key characteristics (convergence, standard/proprietary).
Example answer:
OSPF is link-state, intra-AS, open standard. EIGRP is Cisco hybrid, faster convergence via DUAL, intra-AS. BGP is path-vector, inter-AS (Internet), policy-based.
5. How do you ensure network security in a Cisco-based environment?
Why you might get asked this:
To understand your approach to securing network infrastructure using Cisco-specific features and general best practices.
How to answer:
Mention key security mechanisms: ACLs, port security, AAA, VPNs, firewall policies, secure management (SSH), regular patching, and segmentation (VLANs).
Example answer:
I implement strict ACLs, port security on switches, AAA for device access, configure VPNs, and use Cisco firewalls for traffic inspection. Regular patching and VLAN segmentation are also key.
6. What is the purpose of VLANs and how do you configure them on a Cisco switch?
Why you might get asked this:
Evaluates understanding of Layer 2 segmentation, essential for managing broadcast domains, security, and network organization.
How to answer:
Explain that VLANs segment broadcast domains. Describe configuration steps: create VLAN, assign ports (access/trunk), configure trunking protocol (802.1Q).
Example answer:
VLANs segment broadcast domains for better performance/security. Configure with vlan [ID], assign ports switchport access vlan [ID], and configure trunk ports switchport mode trunk with encapsulation dot1Q.
7. What is an Access Control List (ACL) and how do you apply it?
Why you might get asked this:
Tests knowledge of traffic filtering and basic network security policy enforcement on Cisco devices.
How to answer:
Define ACLs as packet filters. Explain they use permit/deny rules. Describe applying them to interfaces (inbound/outbound) to filter traffic.
Example answer:
ACLs filter traffic based on criteria like IP address/port. You create standard/extended ACLs (access-list or ip access-list) and apply them using ip access-group [ACL_name] [in|out] on an interface.
8. Describe your experience with Cisco IOS and other Cisco operating systems.
Why you might get asked this:
To confirm practical command-line proficiency with the operating systems commonly found on Cisco networking gear.
How to answer:
Discuss your comfort level with the CLI, specific IOS/NX-OS versions you've used, common configuration commands, and any experience with newer OS like IOS XE.
Example answer:
I'm highly experienced with Cisco IOS CLI for routing/switching. I've also worked with NX-OS on Nexus switches in data centers and have some exposure to IOS XE on newer ISR platforms.
9. How do you monitor network performance in Cisco environments?
Why you might get asked this:
Evaluates your knowledge of tools and methods for proactive network management and identifying bottlenecks.
How to answer:
Mention using SNMP-based monitoring tools, NetFlow for traffic analysis, Syslog for events, and built-in commands (show interface, show processes).
Example answer:
I use SNMP tools like SolarWinds or PRTG, NetFlow for traffic patterns, and Syslog for errors/events. I also frequently use show commands on devices to check performance metrics.
10. Can you explain the function of Spanning Tree Protocol (STP)?
Why you might get asked this:
Tests understanding of Layer 2 loop prevention, critical for stable switched networks with redundant paths.
How to answer:
Explain STP's purpose: preventing loops by blocking redundant paths. Mention its role in maintaining a loop-free topology in switched networks.
Example answer:
STP prevents Layer 2 network loops caused by redundant links. It works by blocking specific ports so there's only one active path between any two points, recalculating if the topology changes.
11. How do you configure Quality of Service (QoS) on Cisco devices?
Why you might get asked this:
To assess your ability to prioritize network traffic, ensuring performance for critical applications like voice or video.
How to answer:
Describe the MQC approach: define traffic classes (match criteria), create policy maps (actions like marking, queuing, shaping), and apply service policies to interfaces.
Example answer:
I use MQC: define traffic classes using class-map, create policy maps with actions like priority, bandwidth, shape, and apply them with service-policy [in|out] [policymapname] on interfaces.
12. What is NAT and how does it work?
Why you might get asked this:
Tests understanding of IP address translation, a fundamental technique for conserving public IPs and network security.
How to answer:
Explain NAT translates private to public IPs for Internet access, conserving public addresses. Mention types: Static, Dynamic, and PAT (overload).
Example answer:
NAT translates private IP addresses to public ones. Static maps one-to-one. Dynamic uses a pool. PAT (Port Address Translation) maps many private IPs to one public IP using different port numbers.
13. How would you secure a wireless network?
Why you might get asked this:
Evaluates knowledge of wireless security standards and best practices beyond just Cisco wired networking.
How to answer:
Discuss encryption (WPA3/WPA2), authentication (802.1X with RADIUS), VLANs for guest access, strong passwords, and disabling WPS.
Example answer:
I would use WPA3 or WPA2-Enterprise with 802.1X authentication integrating with a RADIUS server like Cisco ISE. Guest networks should be segmented via VLANs and use separate PSKs.
14. What is HSRP and how does it provide redundancy?
Why you might get asked this:
Tests knowledge of gateway redundancy protocols, essential for high availability at the network edge.
How to answer:
Explain HSRP provides gateway redundancy by presenting a virtual IP/MAC address. Routers are Active/Standby, with Standby taking over on failure.
Example answer:
HSRP allows multiple routers to share a virtual IP and MAC address, acting as a single default gateway. One router is Active, others are Standby, automatically taking over if the Active fails, providing seamless failover.
15. Explain how to set up a site-to-site VPN on Cisco routers.
Why you might get asked this:
Assesses experience with secure tunnel creation, a common task for connecting remote sites.
How to answer:
Outline the process: configure ISAKMP/IKE (Phase 1), IPSec (Phase 2), define interesting traffic (crypto ACL), create crypto map, apply to interface.
Example answer:
Configure Phase 1 (ISAKMP/IKE) policy (encryption, hashing, DH group). Configure Phase 2 (IPSec) transform set. Define interesting traffic with an ACL. Create a crypto map binding Phase 1/2 and ACL. Apply crypto map to the interface.
16. What are the differences between TCP and UDP? When would you use each?
Why you might get asked this:
Tests fundamental understanding of transport layer protocols, crucial for understanding application behavior.
How to answer:
Contrast TCP (connection-oriented, reliable, flow control) with UDP (connectionless, unreliable, faster). Give examples of use cases.
Example answer:
TCP is reliable, connection-oriented, with error correction (HTTP, FTP). UDP is faster, connectionless, no guarantee of delivery (DNS, VoIP, streaming). Use TCP when data integrity is critical, UDP when speed/latency is.
17. How do you troubleshoot a slow network connection?
Why you might get asked this:
Evaluates your methodical approach to diagnosing performance issues beyond simple connectivity.
How to answer:
Mention checking interface errors/drops, bandwidth utilization, latency (ping), path issues (traceroute), QoS settings, and potential congestion points.
Example answer:
I check interface statistics for errors or discards. Measure latency with ping/traceroute. Check bandwidth utilization. Review QoS policies. Look for congestion points or duplex mismatches.
18. How do you recover from a network outage?
Why you might get asked this:
Assesses your ability to act under pressure, prioritizing steps for quick service restoration and communication.
How to answer:
Describe steps: assess scope, identify affected systems, isolate fault, check power/links, review logs, use backup/failover where possible, communicate status.
Example answer:
First, determine the impact scope. Identify the faulty component. Check physical connections and power. Review logs. Utilize redundancy (failover). Restore/replace failed equipment. Communicate updates until resolved.
19. What is DHCP relay and when is it useful?
Why you might get asked this:
Tests understanding of essential network services and how to support them across different subnets.
How to answer:
Explain it forwards DHCP requests across subnets to a centralized server. Useful when the DHCP server isn't on the same subnet as the clients.
Example answer:
A DHCP relay agent forwards DHCP requests from clients on one subnet to a DHCP server located on a different subnet. It's useful to centralize DHCP management in a routed network environment.
20. What causes packet loss and how do you troubleshoot it?
Why you might get asked this:
Evaluates understanding of common network impairments and diagnostic techniques.
How to answer:
List causes (congestion, errors, hardware issues, loops) and troubleshooting steps (check interface stats, cabling, congestion points, monitoring).
Example answer:
Packet loss can be caused by congestion, interface errors, faulty cabling, or network loops. I troubleshoot by checking interface statistics, verifying cabling, monitoring traffic loads, and using ping/traceroute.
21. How do you stay updated on networking trends?
Why you might get asked this:
To gauge your commitment to continuous learning in a rapidly evolving field.
How to answer:
Mention specific resources: vendor certifications (Cisco), technical blogs, industry news sites, webinars, conferences, reading RFCs.
Example answer:
I regularly follow networking blogs and news sites like Network World, read vendor documentation and white papers, work towards certifications, and attend relevant webinars and conferences.
22. What is Software-Defined Networking (SDN)?
Why you might get asked this:
Tests knowledge of modern networking paradigms beyond traditional hardware-centric approaches.
How to answer:
Explain SDN separates the control plane from the data plane, allowing centralized management and automation via controllers and APIs.
Example answer:
SDN decouples the control plane (decides where traffic goes) from the data plane (forwards traffic). A central controller manages the network programmatically, allowing for greater automation and flexibility.
23. Describe a complex network solution you implemented and challenges faced.
Why you might get asked this:
A behavioral/situational question to understand your practical experience, problem-solving skills, and ability to handle complexity.
How to answer:
Choose a specific project. Describe the goal, your role, the technical components (Cisco), challenges encountered (technical, logistical), and how you overcame them.
Example answer:
I led the implementation of a multi-site SD-WAN connecting 10 branches. Challenges included integrating legacy WAN links and routing complexity. We overcame this by phased migration and extensive testing.
24. How do you handle network redundancy and failover configurations?
Why you might get asked this:
To ensure you understand high availability principles and their implementation using Cisco features.
How to answer:
Mention common protocols/techniques: HSRP/VRRP/GLBP for gateways, STP for switched paths, redundant links, and dynamic routing for path failover.
Example answer:
I implement redundancy using HSRP for default gateways, Spanning Tree Protocol on switches, and redundant physical links. Dynamic routing protocols (like OSPF or EIGRP) ensure fast failover between redundant paths.
25. What tools do you use for automating Cisco network tasks?
Why you might get asked this:
Tests your familiarity with network automation, an increasingly important skill.
How to answer:
List specific tools or methods: Python scripting (Netmiko), Ansible, Cisco DNA Center automation, EEM scripts.
Example answer:
I use Python with libraries like Netmiko for configuration deployment and gathering data. I've also used Ansible playbooks for configuration management and have explored Cisco DNA Center's automation features.
26. Explain BGP basics and how you set up BGP?
Why you might get asked this:
Fundamental for roles interacting with the Internet or managing large enterprise networks with multiple connections.
How to answer:
Explain BGP as an exterior gateway protocol. Describe setup: define AS, neighbors (eBGP/iBGP), advertise networks, and apply route policies.
Example answer:
BGP is a path-vector protocol used between autonomous systems (AS) on the Internet. Setup involves defining the local AS, configuring neighbors, advertising your networks, and applying route-maps for policy control.
27. What is the function of the show interface command?
Why you might get asked this:
A basic but essential command, asking about it confirms fundamental troubleshooting skills.
How to answer:
Explain it displays interface status (up/down), line protocol status, encapsulation, IP address, traffic counters, errors, and drops.
Example answer:
The show interface command displays operational status (up/down), link health, configured encapsulation, IP addresses, traffic statistics (packets, bytes), errors, and drops on a specific or all interfaces.
28. What challenges exist when integrating legacy systems with modern networks?
Why you might get asked this:
To understand your awareness of common integration headaches and potential solutions.
How to answer:
Mention protocol incompatibility, security vulnerabilities in older systems, lack of modern management interfaces, and potential performance issues.
Example answer:
Challenges include incompatible protocols, security gaps in older OS, lack of API support for automation, and potential performance bottlenecks. It often requires translation gateways or phased migration strategies.
29. How do you ensure compliance with industry standards and regulations?
Why you might get asked this:
Relevant for roles in regulated industries (finance, healthcare) or those focused on security best practices.
How to answer:
Discuss staying updated on standards (NIST, ISO, GDPR), implementing security controls, regular audits, documentation, and using compliance-focused tools.
Example answer:
I ensure compliance by adhering to established security frameworks (like NIST/ISO 27001), configuring devices securely based on hardening guides, performing regular vulnerability scans, and maintaining detailed documentation of network policies.
30. How do you configure VLAN trunking on Cisco switches?
Why you might get asked this:
Tests practical Layer 2 configuration skills, crucial for connecting switches and carrying multiple VLANs.
How to answer:
Describe the steps: configure port mode as trunk, specify encapsulation (802.1Q), and optionally limit allowed VLANs.
Example answer:
On the desired port, I configure switchport mode trunk. I specify the encapsulation type using switchport trunk encapsulation dot1Q. Optionally, I limit allowed VLANs with switchport trunk allowed vlan [IDs].
Other Tips to Prepare for a cn interview questions
Mastering these 30 cn interview questions is a fantastic start, but comprehensive preparation for cn interview questions involves more. Practice articulating your answers clearly and concisely. Use the STAR method (Situation, Task, Action, Result) for behavioral or scenario-based cn interview questions. As network engineer and tech leader Vint Cerf said, "Technology is the easy part, people are the hard part." Practice explaining complex technical concepts in simple terms, as if to a non-expert. Consider using tools to refine your delivery. Verve AI Interview Copilot at https://vervecopilot.com can provide real-time feedback on your responses to cn interview questions, helping you improve clarity and confidence. Simulating cn interview questions scenarios is invaluable. Verve AI Interview Copilot offers tailored practice based on common technical and behavioral questions. Utilizing Verve AI Interview Copilot for your cn interview questions preparation can give you a significant edge. Remember, consistent practice tackling cn interview questions is key to success.
Frequently Asked Questions
Q1: How technical should my answers be for cn interview questions?
A1: Balance technical depth with clarity. Show you understand the concepts and configuration steps without getting lost in excessive jargon.
Q2: Should I mention certifications like CCNA/CCNP for cn interview questions?
A2: Yes, definitely mention relevant Cisco certifications as they validate your knowledge base for cn interview questions.
Q3: Is it okay to say "I don't know" to a cn interview questions?
A3: Yes, but follow up by explaining how you would find the answer or the resources you would use to troubleshoot the cn interview questions.
Q4: How much experience is needed for these cn interview questions?
A4: The depth of expected answers depends on the role's seniority; entry-level needs basic understanding, senior roles require detailed implementation experience.
Q5: Should I prepare for scenario-based cn interview questions?
A5: Yes, be ready for "How would you troubleshoot X?" or "Design a solution for Y?" questions, applying your knowledge from these common cn interview questions.
Q6: How can I practice for cn interview questions?
A6: Review key concepts, use Cisco Packet Tracer or GNS3 for lab practice, and use interview preparation tools like Verve AI Interview Copilot.
