CCNA Tutorials, Practice Labs & Lab Challenges

We have many tutorials and practice labs on our site to assist you in grasping the concept of the CCNA exam. We have summarized them here in one place and categorized them into specific topics, making it easier for you to learn.

================== CCNA Tutorials ==================

 

================= CCNA Practice Labs =================

Practice labs help individuals and professionals gain practical experience with networking technologies by configuring routers & switches on the emulators

 

================ CCNA Lab Challenges ================

Lab Challenges require you to configure or troubleshooting preconfigured labs

What is SDN?

Most traditional devices use a distributed architecture, in which each control plane is resided in a networking device. Each device will make its own decision. Therefore they need to communicate with each other via messages to work correctly.

In contrast to distributed architecture, centralized (or controller-based) architectures centralizes the control of networking devices into one device, called SDN controller. This is also the main idea when creating SDN. In other words, SDN creates a king to control the whole networking kingdom!

king_chess.jpg

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How a router makes a forwarding decision

We all know when a packet reaches a router interface, the router will send the packet to the destination. But how can a router determines which route is the best to use to send the packet? In this tutorial we will learn more about how a router makes the forwarding decision.

introduction.jpg

To make the routing decision, the router must first build a table which contains all the best routes. When the packets arrive, the router just needs to check this table to choose the best match. This is called the routing table.

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Configure SSH for Remote Access on Cisco Router

One of the most popular way to access a Cisco router remotely is using Telnet but it is an unsecured method as the data is sent unencrypted. If a bad person grabs data from a Telnet session, he can see details like a user’s username and password, giving them access to your router.

SSH (Secure Shell) is a secure method for remote access as it includes authentication and encryption. To do this, it uses a RSA public/private keypair. In this tutorial we are going to learn how to configure SSH for R1 to accept remote SSH access with the topology below.

SSH_topology.jpg

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Key Security Concepts Tutorial

In the digital world, where we use computers and the internet for many things, keeping our information safe is one of the most important tasks. This tutorial will explore some of the popular and important security concepts, making it easier for us to understand and use them to keep our online world secure and private.

Let’s take an example of a common house, which is typically made from bricks, stones, or concrete blocks. They are very strong materials which are considered to be secure from theft. But a house cannot be used easily without doors and windows so that the owners can come in and go out with keys. But it means anyone else can too with some hand tools. The doors and windows (and chimney) are considered vulnerabilities. In cybersecurity, a vulnerability refers to a weakness or flaw in a system’s design, implementation, or operation that could be exploited by attackers to compromise the system’s security.

vulnerabilities.jpg

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Forwarding per-hop behavior (PHB) for QoS Tutorial

Quality of Service (QoS) is a tool that allows our network to prioritize certain types of traffic. QoS defines the actions that a device can apply to a message between the time it enters the device until it exits the device. These actions are called per-hop behaviors (PHBs). With PHBs, we can discard, delay, or even change the header field of each packet. The goal of a PHB is to provide a specified amount of network resources to a class of traffic on a contiguous network.

PHB uses a set of codepoints to mark packets with different levels of priority. These codepoints are embedded in the Differentiated Services Code Point (DSCP) field of the Type Of Service (ToS) field of the IP header.

DSCP.jpg

The key components of PHB are listed below:

+ Classification: When receiving a packet, the first thing a networking device does is to examine the packet’s header to determine what kind of data is inside. This is called classification and involves categorizing network traffic into different groups based on specific criteria like IP address, protocol, port, or application type. An example of classification is shown below:

class-map match-all CLASSIFICATION_HTTP
 match access-group 100
!
access-list 100 permit tcp any any eq 80

In this example, we have created a class map named “CLASSIFICATION_HTTP” that matches all traffic matching access-group 100. Access-group 100 permits TCP traffic with destination port 80.

+ Marking: A packet can be classified when entering or leaving a device but there may be many other devices on its journey to the destination and this repeated process is time-consuming. A more efficient way is to classify the packets once as close to the source as possible and mark them to a QoS standard. This is called marking, which is the process of changing the packet’s header so that other devices know which level (quality) of service should be applied to the packets by just reading the marking. With IP packets, we can mark with either a precedence or DSCP value.

An example of marking is shown below:

policy-map MARKING_HTTP
 class CLASSIFICATION_HTTP
  set dscp af21
!

In this example, we have created a policy map named “MARKING_HTTP” that marks all traffic matching the “CLASSIFICATION_HTTP” class with DSCP value of “af21”.

Apply (activate) the policy-map to an interface:

interface FastEthernet0/1
 service-policy output MARKING_HTTP
!

In this example, we have applied the “MARKING_HTTP” policy map to FastEthernet0/1 interface for outbound traffic.

+ Queuing: the process of holding packets in a queue and scheduling their transmission based on priority. Utilizing algorithms such as Weighted Fair Queuing (WFQ), this process ensures high-priority packets are transmitted before their low-priority counterparts.

An example of configuring queuing is shown below:

interface FastEthernet0/1
 priority-queue out

+ Congestion: occurs when network bandwidth is insufficient to accommodate all traffic. PHB includes mechanisms like Random Early Detection (RED) to manage congestion by discarding low-priority packets before higher-priority ones.

+ Policing: involves monitoring network traffic and enforcing predetermined traffic rate limits. Packets exceeding specified rate limits may be discarded or marked with a lower priority.

+ Shaping: Shaping is the control of the rate at which packets enter the network, preventing congestion and ensuring timely transmission of all packets. Excess traffic is stored in a buffer and released at a controlled rate, shaping the traffic to conform to the desired profile. Shaping is a more gentle approach that attempts to smooth out bursts of traffic. Traffic shaping is applicable only on outbound interfaces as buffering and queuing happens only on outbound interfaces

traffic_policing_vs_shaping.jpg

The figure above shows the difference between Policing and Shaping. With traffic policing, excess traffic is usually dropped while with traffic shaping, excess traffic is buffered and sent again with a little delay.

Port Security Tutorial

By default, all interfaces on a Cisco switch are in an enabled state, meaning that anyone can potentially connect to your network through a wall socket, posing a security risk. Port Security is a feature that enhances the security of Cisco switches by controlling access to Ethernet ports based on the MAC addresses of connected devices.

To address this vulnerability, Port Security allows network administrators to associate only specific MAC addresses with each switch port. This association restricts access to the interface, ensuring that only authorized devices with recognized MAC addresses can use it. If an unauthorized device attempts to connect, you can configure the switch to take predefined actions, such as discarding the incoming traffic, sending a warning message or shutting down the port to mitigate the security threat.

In the figure below, only host with MAC address of AAA (just for example. In fact the MAC address must be 48 bits) was configured to connect to the switch port while other MAC addresses are blocked:

Port_Security_Topo.jpg

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Puppet Tutorial

Besides Ansible and Chef, Puppet is another automation tool in CCNA certification so in this tutorial we will learn about it.

Puppet is built on server-client architecture which comprises a master (centralized server) and some/many nodes (clients). In each node, a Puppet Agent is installed to communicate with the Puppet Master. Puppet Master is the place where all Puppet codes are written and stored. These codes dictate the instructions for performing various tasks for the client. If the Clients need something, they simply request them.

Puppet is based on a Pull deployment model, where the nodes check in regularly after every 1800 seconds with the Master to see if anything needs to be updated in the agent. If anything needs to be updated the agent pulls the necessary Puppet codes from the Master and performs required actions.

Pull_Model.jpg

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