CCNA Prep Packet Tracer Lab 2: Examining Network Traffic Using ‘Simulation Mode’
The second lab I completed in packet tracer required me to use simulation mode for the first time and reinforce the function of the different layers in the OSI model.
Part one clarified the meaning of the G0/0, G0/2, and F0/1 Labels running along the connection lines between the devices in the diagram. They indicate the network interfaces to connect the devices.
The G stands for gigabit (1000Mbps) speeds and the F for fast ethernet (100Mbps).
The network addresses are listed at the top, 192.168.2.0/24, and 10.0.0.0/24. The small numbers next to the devices represent the IP address of that device within that subnet. for example, SRV1’s IP address will be 192.168.1.100.
This helped me to understand how to read a network diagram, now it was time to activate simulation mode.
Within simulation mode, I could view the traffic to get more detailed information and see the 7 layers of the OSI model within the packet tracer for the first time.
You can also notice that the source of my device is a switch, and switches are layer 2 devices which is why the layers above are blank. If I select a router this will change to layer 3.
I wanted to see all of the layers so I needed to navigate to one of the PCs that would be working with layer 7 of the OSI model, the application layer. PC1 is using DHCP to automatically obtain an IP address. To generate some DHCP traffic, which is a layer 7 protocol, I released PC1’s current IP address and then renew it.
From PC1’s desktop, I used a command prompt to release and renew the IP address.
Using the ipconfig and ipconfig /release commands, I generated DHCP traffic to view. I also used the ipconfig /renew command to obtain a new IP.
As you can see, we can see all the way up to layer 7, but 6 and 5 are missing. This is because we are using the TCP/IP model so layers 5, 6, and 7 are all combined into a single layer known as the application layer. These two layers are simply part of layer 7 now.
In conclusion, this lab improved my understanding of how the OSI and TCP/IP models within a network environment, and gave me a chance to use some of my windows command line knowledge to generate network traffic.
