Are you preparing for your CCNA interview in 2025? Whether you’re applying for your first networking role or upgrading your IT career, this blog post covers the top 20 CCNA interview questions and answers that are commonly asked in real-world interviews.
These questions are up-to-date with the latest CCNA 200-301 exam topics and written in a human-friendly format to help you understand and remember better.
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1. What is the purpose of the OSI model?
Answer: The OSI model is a conceptual framework used to understand and standardize the functions of a telecommunication or networking system in seven layers: Physical, Data Link, Network, Transport, Session, Presentation, and Application.
2. What is the difference between a switch and a router?
Answer: A switch operates at Layer 2 (Data Link layer) and connects devices within the same network. A router operates at Layer 3 (Network layer) and connects different networks.
3. Explain the use of VLANs.
Answer: VLANs (Virtual LANs) logically segment a network into separate broadcast domains, improving performance, security, and manageability.
4. What is PortFast in Cisco switches?
Answer: PortFast is a feature that allows a port to bypass STP states and move directly to forwarding, typically used on access ports connected to end devices.
5. What is the purpose of BPDU Guard?
Answer: BPDU Guard disables a port if it receives a BPDU, protecting the network from loops caused by misconnected switches.
6. How does ARP work?
Answer: ARP (Address Resolution Protocol) maps an IP address to a MAC address in a local network so that devices can communicate.
7. What is a default gateway?
Answer: A default gateway is a router that forwards traffic from a local network to other networks or the internet.
8. Explain the difference between TCP and UDP.
Answer: TCP is connection-oriented and reliable, while UDP is connectionless and faster but less reliable.
9. What are the differences between static and dynamic routing?
Answer: Static routing is manually configured, while dynamic routing uses protocols like OSPF or EIGRP to automatically find the best path.
10. What is a broadcast domain?
Answer: A broadcast domain is a network segment where a broadcast packet is forwarded to all devices.
11. What is the purpose of STP (Spanning Tree Protocol)?
Answer: STP prevents network loops by blocking redundant paths in a switch-based network.
12. What is a MAC address?
Answer: A MAC address is a unique hardware identifier assigned to a network interface card (NIC) for communications at the data link layer.
13. What is NAT (Network Address Translation)?
Answer: NAT allows private IP addresses to be translated into public IPs to enable internet access.
14. What is the difference between IPv4 and IPv6?
Answer: IPv4 uses 32-bit addressing while IPv6 uses 128-bit, allowing for a vastly larger number of addresses.
15. What is a subnet mask?
Answer: A subnet mask divides an IP address into a network and host portion, helping routers identify the network portion.
16. What is DHCP?
Answer: DHCP (Dynamic Host Configuration Protocol) automatically assigns IP addresses to devices on a network.
17. What is DNS and how does it work?
Answer: DNS (Domain Name System) translates domain names like google.com into IP addresses.
18. What are access control lists (ACLs)?
Answer: ACLs are filters applied to network traffic to permit or deny packets based on rules.
19. What is the purpose of a trunk port?
Answer: A trunk port carries traffic for multiple VLANs across switches using tagging protocols like 802.1Q.
20. What tools would you use to troubleshoot a network issue?
Answer: Common tools include ping, traceroute, show commands (e.g., show ip interface brief), Wireshark, and logs.
Final Tips for Your CCNA Interview
- Practice commands in a Cisco Packet Tracer or GNS3 lab.
- Understand the logic behind concepts, not just definitions.
- Review real-world scenarios and be ready to explain configurations.
