CCNA Routing and Switching Interview Questions [Updated 2025]
Wednesday, May 21, 2025
If you want to start a career in the network infrastructure industry, pursuing Cisco’s CCNA certification is the best decision you can make. Expanded as Cisco Certified Network Associate (CCNA), it creates a basic foundation for building a solid career as a Network Engineer.
Whether you’re upskilling from the role of a Desktop Support Engineer or want to start out as a Network Engineer, opting for CCNA is mandatory. In fact, 90% of recruiters look for certified candidates.
Preparing for a CCNA interview? Check out this comprehensive guide on best CCNA Routing and Switching interview questions along with answers.
CCNA Routing and Switching Interview Questions for Freshers
What do you understand by networking?
A network is a collection of computers that can communicate with each other and share information. Networking is the practice of connecting computers, devices or systems to share resources and information.
The following areas are covered under the networking umbrella:
Types of Computer Networking
Local Area Network (LAN): Networks limited to a small geographic location such as a home, office, or campus
Wide Area Network (WAN): Networks covering large geographic areas, such as the internet
Metropolitan Area Network (MAN): Networks that cover a city or large campus
Personal Area Network (PAN): Small networks for personal devices, usually employing Bluetooth
Key Networking Concepts
IP Addressing: The process that gives unique addresses to devices on a network
Routing: Where the data takes its route from source to destination
Protocols: Instructions that control how devices talk to each other (TCP/IP, HTTP, etc.)
Network topology: Physical and logical structure of network components
What is meant by routing protocol? What are its important functions?
A routing protocol refers to the set of rules and algorithms used by network devices, especially routers use to talk to each other. It also helps in determining the best path for data to travel across the network.
The following are the most commonly used routing protocols:
RIP (Routing Information Protocol): A lightweight distance-vector protocol with hop count as its metric
OSPF (Open Shortest Path First): A link-state protocol that determines shortest paths from total link cost accumulation
BGP (Border Gateway Protocol): Operated mostly between various autonomous systems on the web
EIGRP (Enhanced Interior Gateway Routing Protocol): A Cisco-owned protocol that integrates the features of distance-vector and link-state protocols
The following are the most important functions of routing protocols:
Deciding optimal path
You can use routing protocol to calculate optimal routes for data packets. This can be accomplished on the basis of the following metrics:
Hop count
Bandwidth
Delay
Reliability
Convergence
Routing protocols can adapt to network changes such as failed links or added routers. These protocols do so by updating routing tables.
Exchanging information
Routers use routing protocols to share information and knowledge about network structure and connectivity between them in a network topology.
Prevention of loops
The routing protocols make sure that the data packets do not revolve around through a network endlessly.
3. Explain the difference between router and switch.
Router | Switch |
A router functions at Layer 3 (Network layer. | A switch is at Layer 2 (Data Link layer) of OSI. |
It relays data between various networks on the basis of IP addresses. | It transfers data by matching MAC addresses in a local network. |
Routers link independent networks and decide the optimal path for data to follow. | It establishes a network by bridging devices within the same broadcast domain. |
4. What are VLANs and why are they used?
A VLAN or Virtual Local Area Network is a group of network topologies that consist of devices that are in different locations physically. You must note that these devices can be remote in position but still act similarly. VLANs are local subdivisions of a switch.
They’re used to do the following:
To improve security through traffic segregation
To minimize broadcast domains
Networks should be structured by department, function, or project
To minimize network management
Performance improvement through elimination of unnecessary traffic
What is the role of ARP protocol?
Address Resolution Protocol (ARP) is a protocol that converts IP addresses to MAC addresses. Here’s the process of how this happens:
Whenever a device wants to communicate with some other device on the local network, it needs the MAC address of the device to create a proper formatted frame.
A broadcast message is sent by ARP protocol asking "Who has this IP?" and the device with that IP responds with its MAC address.
6. What is meant by default gateway? Why is it important?
A default gateway is the router interface to which devices forward packets when they attempt to reach addresses on foreign networks. It is significant because without it, devices can only exchange data within their own local network. The default gateway sets the path for devices to exchange data with foreign networks, such as the internet.
7. What is the difference between static and dynamic routing?
Static Routing | Dynamic Routing |
Static routing requires manual routing table configuration on routers. | Dynamic routing employs protocols (such as OSPF, RIP, EIGRP) to dynamically learn about network destinations. |
Administrators have to specifically configure the routes packets have to follow. | It can modify routes when the network topology is modified. |
It's easy to set up but fails to adapt to network changes. | The routers communicate with each other regarding available paths and path status so that automatic adaptation to changing networks can occur. |
8. What is the function of a spanning tree protocol (STP)?
The main role of STP protocol is to prevent loops in switched networks. It does so by doing the following:
Detection of redundant links in the network
Shutting down some of those links to form a loop-free logical topology
Provisionally reconfiguring the network in case of link failure
If STP were not there, broadcast storms would happen, leading to serious network congestion and breakdowns in cases of redundant links.
9. What is DHCP? How Does it Work?
Commonly called as DHCP, Dynamic Host Configuration Protocol plays the role of automatically assigning IP addresses and other important network configuration parameters such as IP addressing, network protocols, hostname, network topology, bandwidth and more.
This process follows a four-step exchange which is commonly called DORA. Here is how it works:
Discover: Client sends a request for an IP address
Offer: DHCP server provides a free IP address
Request: Client requests the provided IP address
Acknowledgment: Server acknowleges and completes the assignment
This does away with manually setting IP addresses on every device.
10. What are ACLs? How are they important?
You can consider Access Control Lists (ACLs) as a filter system in a network topology. They are a set of rules that filter traffic based on some specific criteria such as:
source/destination IP address
Port numbers
Protocols
They’re important because of the following reasons:
They enhance network security by controlling what traffic is allowed
They can restrict access to sensitive network resources
They help implement network policies
They can be used to prioritize certain types of traffic
CCNA Routing and Switching Interview Questions for Experts
11. Explain the difference between distance vector and link-state routing protocols. When would you choose one over the other?
Distance vector routing protocols (e.g., RIP) use a "routing by rumor" approach. Each router only informs its neighbors of its known routes and the associated distance (hop count). They rely on periodic updates, which can lead to slow convergence and routing loops. Link-state routing protocols (e.g., OSPF, IS-IS) build a complete map of the network. Each router floods link-state advertisements (LSAs) containing information about its directly connected links. This allows routers to calculate the shortest path independently.
When it comes to small and stable networks with limited resources, distance vector protocols are a better choice. It is so because they are simpler to configure and thus, suitable for such networks.
On the other hand, link-state protocols provide faster convergence, better scalability, and loop prevention mechanisms, making them ideal for larger, more complex networks. The choice depends on network size, stability requirements, and available hardware resources.
12. How does Spanning Tree Protocol (STP) prevent loops in a switched network? Explain the process of root bridge election and port states.
STP prevents loops by logically blocking redundant paths in a switched network. It achieves this by electing a root bridge, which acts as the reference point for all other switches. The switch with the lowest bridge ID (priority and MAC address) becomes the root bridge.
The process involves the exchange of Bridge Protocol Data Units (BPDUs). Each switch compares the BPDUs it receives and determines the best path to the root bridge. Ports are then assigned different states:
Root Port: The port on a non-root bridge with the best path to the root bridge.
Designated Port: The port on a segment that is deemed to be the best to forward traffic towards the root bridge.
Blocked Port: A port that is blocked to prevent loops.
Therefore, STP prevents broadcast storms and MAC address table instability by ensuring that a single logical path is active.
13. How VLANs improve network security and performance. What are the different types of VLANs? Name them with a simple explanation.
VLANs (Virtual LANs) segment a physical network into multiple logical networks. This improves security by isolating traffic between VLANs, preventing unauthorized access. They also enhance performance by reducing broadcast traffic within each VLAN, preventing it from flooding the entire network.
Types of VLANs include:
Data VLAN: Carries user-generated traffic.
Voice VLAN: Prioritizes voice traffic for quality of service.
Management VLAN: Used for managing network devices.
Native VLAN: Transports untagged traffic on trunk links.
14. Explain the concept of routing tables and how they are used to forward packets.
A routing table is a database on a router that keeps information regarding known networks and the optimal path to reach them. The destination network, the next-hop IP address, and the metric (cost) of the path are contained in each entry in the routing table.
When a router receives a packet, it consults its routing table. It searches for the most specific route that matches the destination IP address of the packet. The router then forwards the packet to the next-hop IP address specified in the routing table entry. The packet is typically dropped or forwarded to a default gateway if no matching route is identified.
15. Discuss the different types of switching techniques.
There are mainly three different types of switching techniques:
Store and forward
Cut-through
Fragment-free
Each of them are explained one by one as follows:
Store-and-Forward: The switch receives the entire frame, checks it for errors using the FCS (Frame Check Sequence), and then forwards it. Provides high error detection but higher latency.
Cut-Through: The switch starts forwarding the frame as soon as it reads the destination MAC address. This lowers latency but forwards potentially faulty frames.
Fragment-Free: The switch reads the first 64 bytes of the frame before forwarding. This checks for collisions, as most collisions occur within the first 64 bytes. It is a compromise between latency and error checking.
16. What are the advantages and disadvantages of using static routing vs. dynamic routing?
Static Routing Advantages: Simplicity, security (less prone to routing protocol attacks), predictability.
Disadvantages: Manual configuration, lack of adaptability to network changes, scalability issues.
Dynamic Routing Advantages: Automatic adaptation to network changes, scalability, reduced administrative overhead.
Disadvantages: Higher complexity, security vulnerabilities, resource intensive (CPU, memory).
17. How does OSPF (Open Shortest Path First) handle network changes and ensure fast convergence?
OSPF employs a link-state database to keep an up-to-date map of the network. When there is a change in the network (e.g., a link goes down), the router recognizes the change and floods an LSA to all other routers in the area. These routers update their link-state databases and recompute the shortest paths through use of the SPF algorithm.
This method provides rapid convergence and reduces interference with network traffic. OSPF also supports areas, which confine the boundary of LSAs and enhance scalability.
18. What is the difference between a collision domain and a broadcast domain?
Collision Domain | Broadcast Domain |
Collision domain refers to a network segment consisting of devices that compete for access to shared medium. | A broadcast domain is an area of a network segment to which a broadcast frame is transmitted to every device. |
This competition leads to collisions when two or more devices transmit at the same time. | Broadcasts are not transmitted through router interfaces; routers fragment broadcast domains. |
Hubs create a single collision domain, whereas switches break collision domains by forwarding traffic only to the destination port. | VLANs also provide for the establishment of independent broadcast domains on a switched network. |
19. Describe the purpose of QoS (Quality of Service) and how it can be implemented in a network.
QoS ensures that some network traffic gets preferential treatment over other traffic. It assists in prioritizing mission-critical applications such as voice and video to ensure optimal performance even during congestion.
QoS can be achieved through a number of techniques such as:
Classification and Marking: Marking and labeling traffic on the basis of type or priority.
Queueing: Assigning priority to different queues based on priority.
Congestion Avoidance: Avoiding congestion by discarding or delaying lower-priority traffic.
Shaping and Policing: Restricting the amount of bandwidth consumed by certain traffic streams.
20. Explain the role of FHRPs (First Hop Redundancy Protocols) like HSRP, VRRP, and GLBP in achieving high availability.
Multiple routers can share virtual IP address and MAC address as a default gateway as FHRPs provide fault tolerance.
If the active router fails, it is automatically replaced by a standby router, which reduces downtime and preserves network connectivity.
HSRP (Hot Standby Router Protocol): This protocol is a Cisco-owned router protocol.
VRRP (Virtual Router Redundancy Protocol): This router protocol follows an open standard.
GLBP (Gateway Load Balancing Protocol): This protocol is Cisco proprietary, i.e., it is owned by Cisco. It provides load balancing between multiple routers rather than simply standby.
These protocols enhance robustness by providing redundancy at the first hop router, making the network available round the clock even when routers fail. They are essential for networks demanding high availability.
Conclusion
Routing and switching concepts form the basic foundation for becoming a Network or Network Security Engineer. In this guide, we have added both routing and switching interview questions for beginners and advanced candidates. We’ve added an updated list of the most commonly-asked interview questions. However, you must note that this list is not exhaustive.
