CCNA
Cisco Certified Network Associate certification resources
The EUI-64 Process: How IPv6 Interface IDs Are Generated
When a device configures an IPv6 address through Stateless Address Autoconfiguration (SLAAC), it gets the network prefix, typically a /64, from a Router Advertisement, but it has to generate its own 64-bit Interface ID independently. This guide covers exactly how that generation works: the EUI-64 process that derives an Interface ID from a MAC address,...
Unicast, Multicast, and Broadcast Communication Explained
Every packet that moves across a network is delivered using one of three fundamental communication methods: unicast, multicast, or broadcast. Each defines how many devices receive a given transmission — one, a selected group, or all of them — and choosing the right one is central to how efficiently a network runs. As video streaming,...
Network Prefix, Network Address, Broadcast Address, and Host Address Explained
Every IPv4 subnet has a handful of specific addresses with fixed roles: one identifies the network itself, one is reserved for broadcasting to every device on it, and the rest are available for hosts. This guide covers exactly how to calculate each one, using prefix notation and binary math, with one consistent worked example carried...
Network and Host Portion of an IPv4 Address
Every network needs a unique network number. Every host needs a unique IP address. The IPv4 address is a 32-bit number. It identifies both a network and a host on that network. This split is one of the very first things you learn in networking, and it stays useful for your entire career. We usually...
Positional Number System and Examples
In a positional number system, each symbol represents a different value depending on the position it occupies in a number, and each system has a value that relates to the number directly next to it. The total value of a positional number is the total of the resultant value of all positions. The decimal number...
IPv4 Address Classes Explained: A, B, C, D, and E
An IPv4 address identifies a device on a network, similar to how a street address identifies a physical location. Every device on an IP-based network, including the internet, needs one to communicate. This guide covers the five IPv4 address classes, how to identify each one from its first octet, and the specific network and host...
Cisco Router Interface Configuration: A Complete CLI Guide
Configuring a router’s interfaces correctly is foundational to everything else that router does. A misconfigured or disabled interface means no traffic flows, regardless of how well everything else on the device is set up. This guide covers the full interface configuration process, from selecting the right interface through verification and troubleshooting, using the core commands...
Basic Cisco Router Configuration: Complete Step-by-Step Guide
Different IP networks cannot communicate with each other without a router. Routers do this job by forwarding packets from one IP network to another using routing. Before a router can do any of this, some basic configuration is required. This guide covers the complete basic Cisco router configuration process, using Cisco Packet Tracer for simulation,...
Cisco IOS Command Modes Explained: User EXEC, Privileged EXEC, and Global Configuration Modes
Cisco IOS devices use hierarchical command modes to control access and prevent accidental misconfigurations. Whether you’re managing a router, switch, or preparing for the CCNA exam, understanding these modes is fundamental: Global configuration mode contains a number of sub-configuration modes (also called specific or extended configuration modes). The table below lists common configuration modes and...
Cisco Router Interfaces: Types, Configuration, and Troubleshooting
Every router interface falls into one of two broad categories: physical, where actual traffic enters and exits over real cabling or radio, and logical, which exist purely in software but serve genuinely important roles — a stable router ID, a VPN endpoint, a way to carve one physical port into many logical ones. Knowing which...