CCNA Interview Questions with Answers

OSI Model and Networking Basics

• The OSI model is a conceptual framework with 7 layers that defines how different networking protocols interact.
• It helps in understanding the process of data communication.

Hubs, Switches, and Routers

• A hub operates at the physical layer, broadcasting data to all connected devices.
• A switch operates at the data link layer, forwarding data only to the device that needs it.
• A router operates at the network layer, directing traffic between different networks.

MAC Addresses and Subnet Masks

• A MAC (Media Access Control) address is a unique hardware address assigned to network interfaces for communication within a local network.
• A subnet mask is used to divide an IP address into network and host portions, determining which part identifies the network and which identifies the specific device within that network.

IP Addresses and DHCP

• A static IP address is manually configured and doesn't change, while a dynamic IP address is assigned by a DHCP server and can change over time.
• DHCP (Dynamic Host Configuration Protocol) automatically assigns IP addresses and network configuration settings to devices on a network, simplifying network management.

NAT and ARP

• NAT (Network Address Translation) is used to map private IP addresses to a public IP address for communication over the Internet, allowing multiple devices to share a single public IP.
• ARP (Address Resolution Protocol) maps IP addresses to MAC addresses in a local network, enabling devices to communicate on the same network.

TCP and UDP

• TCP (Transmission Control Protocol) provides reliable, connection-oriented communication.
• UDP (User Datagram Protocol) is connectionless and offers faster but less reliable communication.

Routing and Gateways

• A default gateway is a router that connects devices in a local network to external networks, allowing them to access resources outside the local network.
• A routing table contains information about routes and paths that routers use to determine the best path for forwarding data to its destination.

Routing Protocols and ACLs

• OSPF (Open Shortest Path First) is a link-state routing protocol that calculates the shortest path to reach network destinations using the SPF (Shortest Path First) algorithm.
• ACLs (Access Control Lists) are used to control and filter network traffic based on criteria like source and destination IP addresses, port numbers, and protocols.

Subnetting and VLANs

• Subnetting involves dividing a larger IP network into smaller, more manageable subnetworks, optimizing IP address allocation.
• A VLAN (Virtual Local Area Network) is a logical segmentation of a network, enabling devices to be grouped into separate broadcast domains for security, scalability, and traffic management.