Your first network: a step-by-step CCNA beginner lesson

CCNA stands for Cisco Certified Network Associate. It is a certification for people learning to work with computer networks. A certification exam checks knowledge and skills. It is not something you need to pass before you can begin this course. We start with one small network because it is easier to see why each part matters.

Cisco gives each exam a topic list, also called a blueprint. The current 200-301 v1.1 exam covers network fundamentals (20%), network access (20%), IP connectivity (25%), IP services (10%), security fundamentals (15%), and automation and programmability (10%). These percentages show how the exam topics are weighted. You do not need to understand all six names today.

The current exam is available through 2 February 2027. Version 2.0 starts on 3 February 2027. Choose the official topic list for your planned exam date. Our 60 lessons form a learning order, not a promise that everyone will be exam-ready in 60 days. The weekday release schedule is not a deadline for you. Repeat an example, take a break and ask for help when needed.

• Begin with one clear idea and one small result, not a list of commands to memorize.
• Use the official exam topic list for the date you plan to take the exam.
• Your learning pace can be slower than the course publication schedule.

GNS3 is a program for building practice networks. Its workspace is the area where you place devices and draw their connections. A saved collection of devices and settings is a project. The connection picture is a topology. A node is one device in that picture. These names describe things you can see; they are not extra tasks.

VPCS means Virtual PC Simulator. It behaves like a small computer used for network tests. It is not a full Windows computer and does not have a browser or office apps. We use two instances, meaning two separate copies, named PC1 and PC2. Each has its own address and its own text window for commands.

The built-in Ethernet switch connects the two practice computers. Ethernet is a common technology for carrying information over local links. A port or interface is a connection point. The first port may be numbered zero, so Ethernet0 is a name, not a warning. In this lab, both switch ports stay in one shared access segment: one local connection group.

The switch carries Ethernet frames, which are units of information sent over these links. It does not choose or repair our IP settings. GNS3's built-in switch supports VLAN port modes, which can separate local groups, but we do not change those settings today. This exercise uses only the built-in switch and VPCS, so it needs no Cisco software image.

• A topology shows which device connects to which other device.
• PC1 and PC2 are separate test computers, each with its own console.
• Leave the switch settings unchanged for this first exercise.

Internet Protocol, shortened to IP, provides rules for addressing and moving information across networks. An IP address identifies a network connection. We use IPv4, one version of IP. An IPv4 address has four numbers separated by dots. In 192.168.10.1, read the numbers as 192, 168, 10 and 1. Each number can range from 0 to 255. It is not a decimal fraction.

A subnet is a local IP group. A subnet mask tells the computer where that group's boundary lies. Our mask is 255.255.255.0, also written /24 for IPv4. With this mask, the first three numbers identify the group, while the last number distinguishes the addresses we use inside it. Thus 192.168.10.1 and 192.168.10.2 are local to each other. This shortcut is specific to this mask. Later lessons teach other boundaries.

A router connects different IP networks. A default gateway is usually a router that helps a computer reach other networks when no more specific path applies. Our two computers need no gateway because their addresses share one local group. We deliberately do not connect the lab to the Internet.

A console is a text window for one device. A command is an instruction you type there. The prompt, such as PC1>, identifies the device waiting for input. Type only the command, then press Enter. The ip command sets an address, show ip displays settings, ping asks another device for a test reply, and save keeps settings for later. The lab explains every argument beside its command.

• Read the device name before typing; the same command in the wrong console changes the wrong computer.
• The mask matters as well as the address; compare both with the plan.
• Type spaces and dots exactly as shown, then press Enter after each command.

Troubleshooting means finding why something does not work. Begin with a prediction. In this lab, PC1 should receive replies when it tests PC2. Run the test and compare the result with that prediction. A successful ping is a useful observation, not a guarantee that the Internet or every application works.

Ping uses Internet Control Message Protocol, or ICMP. It sends an echo request, a test message asking for a reply. A reply from the expected address shows that the request and response travelled successfully at that moment. Reply text often includes a time value. The exact wording and timing can vary, so do not demand a perfect copy of someone else's output.

We then change only PC2's address from 192.168.10.2 to 192.168.20.2. With our mask, this puts PC2 outside PC1's group. PC1 has no router or default gateway for that other group. Its test to the new address should fail. Keep the failure text. Read show ip on both devices before changing anything else.

Restore PC2's planned address and return to PC1 to repeat the original test. Testing PC2 from itself is not enough: a self-test need not cross the connection to PC1. If the repeated peer test succeeds, the change and the result support your explanation. If it still fails, inspect the console selection, addresses, running devices and links one at a time.

• Predict the result before running a test, then record what actually happened.
• A failed ping is a symptom; read the settings before deciding its cause.
• After a repair, repeat a test from the other device, not only a self-test.

Use a notebook or a notes app. Give the note the same name as the project, such as CCNA-Day-01. Write the date, the addresses you intended to use and which device ran each test. Then record the result in ordinary language. You can write 'PC1 received replies from PC2' before learning every field in the output.

Keep four short lines for each experiment: I expected; I saw; I changed; I checked again. These are learning notes, not a formal report. If you make a typing mistake, record how you noticed it. That makes the next attempt easier and helps a teacher understand your question. Avoid copying a long screen of output without saying which result matters.

Saving a GNS3 project and saving each VPCS device's settings are different tasks. In each VPCS console, save stores its current configuration in a startup file. A configuration is the set of settings a device uses. Keep the GNS3 project as well, because it contains the devices and their connections. When you reopen the project, start the devices and check their settings rather than assuming everything is correct.

Try the guided version first. On another attempt, cover the commands and explain the next action before revealing them. Use the practice questions before the scored quiz. A wrong answer shows which idea to revisit; it does not mean you cannot learn networking. Do not store real passwords or private customer information in practice notes.

• Record the device, the expected result and the actual result together.
• Save each VPCS configuration as well as keeping the GNS3 project.
• Repeat unclear steps; the release of the next lesson is not your deadline.

An isolated lab has no link to your real home, school or office network. Keep this first project isolated. Do not add a Cloud or NAT node, which can connect a lab to other networks. Do not type the commands into a work router, your phone's settings or the browser address bar. The instructions name the intended VPCS console.

Installation needs a suitable computer and permission from its owner. Start with the official guide for your operating system. Windows and macOS are operating systems: the main software managing a computer. Ask for help if the installer, local server or console does not start. Do not turn off security software or change a shared network to make an exercise work.

This first lesson needs no Cisco software image. An image, in this context, is a file containing device software. Later Cisco labs may need one. GNS3 does not supply those images. A license defines how software may be used, so obtain it through an authorized source and check the terms for the intended platform. Owning a device does not automatically permit every simulated use.

Cisco Modeling Labs, often called CML, is another official way to run Cisco practice labs under its own terms. Do not assume a CML license permits exporting its images into GNS3. You can decide about later software when you reach a lesson that needs it. For now, two VPCS devices, one built-in switch and careful observation are enough. Paper exercises help understanding but do not replace the later hands-on checks.

• Run these commands only in the named practice-device console.
• Use the official installation guide and ask for help instead of disabling security controls.
• No Cisco software purchase or image download is needed for this first lab.