Top 15 CCNA Interview Questions and Answers in 2025

Cisco Certified Network Associate (CCNA) is an entry-level networking certification that verifies your ability to optimize and manage Cisco networking resources inside an organization.

We prepared a CCNA question bank that includes the top 15 commonly asked CCNA questions and answers. Practicing with our CCNA interview questions and answers can help you land the job quickly.

In this CCNA interview guide, we’ve examined and put together the most common CCNA interview questions and answers.

Furthermore, mastering networking skills with our Cisco Training courses can help you answer more of these Cisco CCNA interview questions.

1. What is the difference between a switch and a hub? 

A hub is a simple device that sends data to all the devices connected to it, without the consideration of the recipient. It works on Layer 1 (Physical) and does not inspect the data, resulting in network inefficiencies. A switch works on Layer 2 (Data Link) and sends data only to the particular device (using MAC addresses), reducing network congestion and enhancing performance. Switches can also form VLANs to segment the network, but hubs cannot.

2. What are the various IP address types?

There are various IP address types:

  ● Public IP addresses: These are unique worldwide and employed to address devices on the internet.

● Private IP addresses: Used on local networks and are not routable over the internet (e.g., 192.168.x.x, 10.x.x.x).

  ● Loopback IP addresses: The 127.0.0.0/8 range is reserved for loopback addresses, used by devices to address themselves (e.g., 127.0.0.1).

  ● Multicast IP addresses: Reserved for sending data to many devices on a network (e.g., 224.0.0.0 through 239.255.255.255).

3. What is DNS?
DNS (Domain Name System) is a system that works like a phonebook for the internet. It changes easy-to-remember domain names, like www.example.com, into IP addresses, like 192.168.1.1, that computers use to talk to each other. DNS is very important because it lets people visit websites using names instead of needing to remember number addresses.

4. What is a MAC address?
A MAC (Media Access Control) address is a special number given to a network interface card (NIC). It helps devices talk to each other at the Data Link layer (Layer 2). A MAC address is 48 bits long and shown in hexadecimal format, like 00:1A:2B:3C:4D:5E. It helps find and send data to the right device on a local network.

5. What is ARP (Address Resolution Protocol)?
ARP (Address Resolution Protocol) helps match an IP address to the correct MAC address in a local network. When a device wants to talk to another device on the same network, it sends an ARP request to ask, “Who has this IP address?” The device with that IP replies with its MAC address. This way, the first device knows where to send the data.

6. What is NAT?
NAT (Network Address Translation) changes IP address details in packet headers when data passes through a router or firewall. NAT lets many devices on a private network share one public IP address to go online. It also helps save public IP addresses and hides internal IP addresses for extra security.

7. What is the function of the OSI layer 4 (Transport Layer)?
The Transport Layer (Layer 4) makes sure data is sent and received properly between devices. It takes care of how fast data moves, checks for errors, fixes problems, and breaks data into smaller parts (and puts them back together). Important protocols in this layer are TCP, which is reliable and keeps a connection, and UDP, which is faster but doesn’t keep a connection.

8. What is a default gateway?
A default gateway is the IP address of a router or device that sends data from a local network to other networks, like the Internet. When a device wants to reach another network but doesn’t know the exact path, it sends the data to the default gateway to handle it.

9. Explain the difference between IPv4 and IPv6
IPv4 (Internet Protocol version 4) uses 32-bit addresses, which means it can create about 4.3 billion unique IP addresses. But because the internet has grown so much and more devices are connected now, we have run out of IPv4 addresses.

To solve this problem, IPv6 (Internet Protocol version 6) was created. It uses 128-bit addresses, which gives us a huge number of addresses, about 340 undecillion (a number so big it’s almost unlimited).

Besides offering more addresses, IPv6 has extra features:

• It has built-in security through required IPSec support.
• It doesn’t need NAT (Network Address Translation) like IPv4 does.
• It makes routing easier.
• It improves how multicast works (sending data to multiple devices at once).
• It gives better support for mobile devices.

Also Read: IPv4 vs. IPv6: What Are the Key Technical Differences?

10. What is the purpose of an ACL (Access Control List)?
An ACL (Access Control List) is used to control network traffic that comes in or goes out based on things like IP addresses, protocols, or port numbers. It’s a list of rules added to routers or firewalls to manage how data moves through a network.

ACLs help improve network security by deciding which traffic is allowed or blocked. These decisions are made using details like:

• The source or destination IP address
• The protocol type (like TCP or UDP)
• The port number (like HTTP or FTP)

There are two types of ACLs:

• Standard ACLs: Only look at the source IP address to allow or block traffic.
• Extended ACLs: Look at the source and destination IP addresses, protocols, and port numbers to make more detailed rules.

11. What is the difference between static and dynamic routing?
Static routing means the network administrator sets up the routes manually. It’s usually used in small and stable networks. If the network changes (like a connection goes down), the static routes won’t update automatically — someone has to change them by hand.

Dynamic routing uses routing protocols like RIP, OSPF, and EIGRP to automatically find and update routes. It can quickly react to network changes, like when a router goes offline, and choose a new path. This makes it better for large or complex networks.

12. What is the function of a router in a network?
A router is a device that connects different networks and sends data packets between them. It looks at the destination IP address in each packet and checks its routing table to decide the best way to send the packet.

Routers can use static or dynamic routing protocols (like OSPF or EIGRP) to keep their routing tables updated. They can also provide features like:

• NAT (Network Address Translation) for using private IP addresses
• Firewall protection for security
• Separating broadcast domains, which helps with network segmentation

13. What is the difference between a bridge and a switch?
A bridge connects two parts of a network and filters traffic using MAC addresses at Layer 2 of the OSI model. It was one of the first devices used to split up large networks and reduce traffic problems.

A switch does the same basic job but is more advanced. It has multiple ports, so it can connect many devices and manage traffic more efficiently. A switch can handle thousands of MAC addresses and sends data only to the device it’s meant for, which gives better performance.

14. What is a Layer 3 switch?
A Layer 3 switch is a device that combines features of a Layer 2 switch and a router. It can:

• Switch data using MAC addresses (Layer 2)
• Route data using IP addresses (Layer 3)

Layer 3 switches are often used inside networks to route traffic faster than a traditional router, because they use hardware-based forwarding. This makes them a good choice for large, high-speed networks, especially in the distribution layer.

15. What is the OSI model? Can you explain its layers?
The OSI (Open Systems Interconnection) model is a way to understand how data moves through a network. It breaks down communication into seven layers, from sending raw data through cables to the services used by applications. Each layer has a specific job and works with the layers above and below it.

Here are the seven layers of the OSI model:

● Layer 1 – Physical
This layer deals with the physical connection — like cables, fiber optics, or signals. It sends raw bits (0s and 1s) from one device to another. It also defines electrical and mechanical rules (e.g., voltages, pin layouts).

● Layer 2 – Data Link
This layer makes sure data is sent reliably between two devices on the same network segment. It handles:

• Error detection
• Flow control
• MAC addressing (e.g., used in Ethernet and Wi-Fi)

● Layer 3 – Network
This layer is in charge of routing packets between networks using IP addresses. Devices like routers work at this layer to move data across different networks.

● Layer 4 – Transport
This layer manages end-to-end communication between devices. It breaks data into smaller parts (segmentation) and makes sure it arrives correctly.
Main protocols here:

• TCP (reliable, connection-based)
• UDP (faster, connectionless)

● Layer 5 – Session
This layer sets up, manages, and ends sessions (connections) between two applications. It keeps track of the conversation and knows when to stop it.

● Layer 6 – Presentation
This layer translates, encrypts, and compresses data so it can be understood by the receiving application.
Examples:

• SSL/TLS for encryption
• Changing text formats like ASCII to EBCDIC

● Layer 7 – Application
This is the layer closest to the user. It provides network services to applications like:

• HTTP (for web browsing)
• FTP (for file transfer)
• DNS (for domain name resolution)

Conclusion

Having a solid knowledge base of networking fundamentals is essential to anyone who is preparing to enter networking positions or certifications like CCNA. This guide discussed networking fundamental aspects such as the OSI model, routing types, ACLs, and core networking devices. Mastering these CCNA interview questions and answers and practicing related routing and switching interview questions will increase your confidence and improve your chances of success in both exams and job interviews.