Cisco Packet Tracer Fundamentals

Cisco Packet Tracer Basics

• Introduction to Cisco Packet Tracer (CPT) and its use for creating network labs.
• Objective: Familiarize users with the software interface and basic functionalities.

Creating a Simple LAN

• Accessing Devices:
  • Network devices (routers, switches, hubs, wireless devices, firewalls) are located at the bottom of the CPT interface.
  • End devices (PCs, laptops, servers) can also be selected from the bottom.
• Adding a Switch:
  • Click on network devices, choose a switch (e.g., 2950 24-port switch), and drag it to the workspace.
• Adding Computers:
  • Click on end devices and drag PCs or laptops to the workspace.
• Connecting Devices:
  • Use the "Connections" option (zigzag signal) to connect devices with wires.
  • The software can automatically select the appropriate wire type.
  • A black wire indicates a straight cable connection.
• Initial Login:
  • Choose "Cisco Skills for All" when prompted during CPT startup.
  • Troubleshooting login issues: Close internet, start CPT, then restart the internet.

Practical Exercise: Building a LAN

• Drag a switch and several computers to the workspace.
• Connect the computers to the switch using automatic connection wires.
• Click on each device and then the switch port to establish the connection.

Editing and Deleting Devices

• Deleting Devices:
  • Use the cross symbol at the top to delete devices or connections.
  • Click the cross, then click the item to be deleted.
• Exiting Delete Mode:
  • Use the escape symbol (first icon at the top) to return to the normal cursor.

Adding IP Addresses to Devices

• Adding Labels:
  • Use the clipboard icon to add text labels for IP addresses near each computer.
  • Example IP addresses: 10.0.0.1, 10.0.0.2, 10.0.0.3, 10.0.0.4.
• Configuring IP Addresses:
  • Click on a computer, go to the "Desktop" tab, and select "IP Configuration."
  • Choose "Static" to manually assign an IP address.
  • Enter the IP address (e.g., 10.0.0.1) and subnet mask (e.g., 255.0.0.0 for Class A).
  • Leave the default gateway and DNS server fields blank for a simple LAN.
• Repeat the IP configuration for each computer, incrementing the last octet of the IP address.
• Hover the mouse over a computer to view its configured IP address.

Testing the LAN with Ping

• Accessing Command Prompt:
  • Click on a computer, go to the "Desktop" tab, and select "Command Prompt."
• Using Ping Command:
  • Type ping followed by the destination IP address (e.g., ping 10.0.0.4).
  • Successful replies indicate that the LAN is working correctly.
• Test connectivity by pinging all other computers in the LAN.

Customizing the Packet Tracer Interface

• Showing Port Labels:
  • Go to "Options" > "Preferences."
  • Check the box for "Always show port label in the logical workspace" to display interface names (e.g., FA0/1, FA0/2).
• Adjusting Font Size:
  • In preferences, increase the font size for better visibility.
  • Adjust font sizes for the main interface and CLI for improved readability.

Creating a LAN Using DHCP

• Adding a Server:
  • Drag a server from the end devices to the workspace.
• Configuring the DHCP Server:
  • Assign a static IP address to the server (e.g., 20.0.0.1).
  • Go to the "Services" tab, select "DHCP," and turn the service "on."
  • Configure the DHCP pool: set the default gateway (if needed), start IP address, maximum number of addresses, and DNS server (if needed).
• Configuring Computers to Use DHCP:
  • For each computer, go to "IP Configuration" and select "DHCP."
  • The computer will automatically receive an IP address from the DHCP server.
• DHCP Process (DORA):
  • Discover: Client broadcasts a request for a DHCP server.
  • Offer: DHCP server offers an IP address to the client.
  • Request: Client requests offered IP address.
  • Acknowledge: DHCP server acknowledges and assigns the IP address to the client.

Practical Scenario: DHCP in an Enterprise Network

• Branch Office:
  • A small office with a few computers using a DHCP server for IP address assignment.
• Head Office:
  • A larger office with many users. The company decides to move the DHCP server from the branch office to the head office.
• Problem:
  • After moving the DHCP server, computers in the branch office no longer receive IP addresses.
• Reason:
  • DHCP uses broadcast packets for the discovery process. Routers do not forward broadcast packets by default, thus preventing the DHCP requests from reaching the server in the head office.
• Solution: DHCP Relay Agent
  • Configure a DHCP Relay Agent on the router in the branch office.
  • The Relay Agent converts the broadcast DHCP requests into unicast packets, which can be forwarded to the DHCP server in the head office.
  • The DHCP server then responds to the Relay Agent, which forwards the IP address to the client.

Introduction to Routers

• Connecting a Router and a Computer:
  • Connect a router to a computer using a cable.
• Router Operating System (iOS):
  • Routers use an Internetwork Operating System (IOS).
• Configuration Methods:
  • Command Line Interface (CLI)
  • Graphical User Interface (GUI)
• Focus on CLI configuration first to understand the underlying commands and concepts.

CLI Configuration Modes

• User Mode:
  • Limited functionality, mostly for viewing basic information.
  • Prompt: Router>
• Privileged Mode:
  • Allows more advanced commands and configuration.
  • Enter by typing enable
  • Prompt: Router#
• Configuration Mode:
  • Used to configure router settings.
  • Enter by typing config terminal or config t
  • Prompt: Router(config)#
• Configuration Interface Mode:
  • Used to configure specific interfaces.
  • Enter by typing interface <interface-name> (e.g., interface FastEthernet0/0)
  • Prompt: Router(config-if)#

Basic Router Configuration

• Accessing CLI:
  • Click on the router, then go to the "CLI" tab.
• Navigating Configuration Modes:
  • Type enable to enter privileged mode.
  • Type config terminal to enter configuration mode.
  • Type interface <interface-name> to enter interface configuration mode.
• Assigning an IP Address to an Interface:
  • Use the command ip address <ip-address> <subnet-mask> in interface configuration mode (e.g., ip address 10.0.0.1 255.0.0.0).
• Enabling an Interface:
  • By default, interfaces are in a shutdown state.
  • Use the command no shutdown to enable the interface.
• Exiting Configuration Modes:
  • Use the command exit to move one step back.

Example Configuration

• Configuration Steps:
  • Enter privileged mode: enable
  • Enter configuration mode: config t
  • Enter interface configuration mode: interface FA0/0
  • Assign IP address: ip address 10.0.0.1 255.0.0.0
  • Enable interface: no shutdown
  • Exit interface configuration mode: exit
  • Exit configuration mode: exit
• Configuring the Computer:
  • Assign a static IP address (e.g., 10.0.0.2) and subnet mask (e.g., 255.0.0.0).
  • Set the default gateway to the router's IP address (e.g., 10.0.0.1).
• Testing Connectivity:
  • Use the ping command on the computer to ping the router's IP address.
  • Use the ping command on the router to ping the computer's IP address.

GUI Configuration

• Accessing GUI:
  • Click on the router, then go to the "Config" tab.
• Configuring Interfaces:
  • Select the interface (e.g., FastEthernet0/0) in the GUI.
  • Check the "Port Status" box to enable the interface (equivalent to no shutdown).
  • Enter the IP address and subnet mask in the appropriate fields.
• GUI simplifies the configuration process, but CLI is essential for advanced configurations and troubleshooting.