My Mini Project Essay
Graphical Network Simulator What is GNS3? GNS3 is a graphical network simulator that allows simulation of complex networks. To provide complete and accurate simulations, GNS3 is strongly linked with: * Dynamips, a Cisco IOS emulator. * Dynagen, a text-based front end for Dynamips. * Qemu, a generic and open source machine emulator and virtualizer. * VirtualBox, a free and powerful virtualization software. GNS3 is an excellent complementary tool to real labs for network engineers, administrators and people wanting to study for certifications such as Cisco CCNA, CCNP, CCIP and CCIE as well as Juniper JNCIA, JNCIS and JNCIE.
It can also be used to experiment features of Cisco IOS, Juniper JunOS or to check configurations that need to be deployed later on real routers. Thanks to VirtualBox integration, now even system engineers and administrators can take advantage of GNS3 to make labs and study for Redhat (RHCE, RHCT), Microsoft (MSCE, MSCA), Novell (CLP) and many other vendor certifications. This project is an open source, free program that may be used on multiple operating systems, including Windows, Linux, and MacOS X. Introduction to GNS3: GNS3 is a Graphical Network Simulator that allows emulation of complex networks.
You may be familiar with VMWare, VirtualBox or Virtual PC that are used to emulate various operating systems in a virtual environment. These programs allow you to run operating systems such as Windows XP Professional or Ubuntu Linux in a virtual environment on your computer. GNS3 allows the same type of emulation using Cisco Internetwork Operating Systems. It allows you to run a Cisco IOS in a virtual environment on your computer. Dynamips is the core program that allows IOS emulation. GNS3 runs on top of Dynamips to create a more user friendly, graphical environment.
GNS3 also supports other emulation programs, namely Qemu, Pemu and VirtualBox. These softwares are used to emulate Cisco ASA and PIX firewalls, Cisco IPS, Juniper routers as well as hosts (Linux, Windows, Mac OS X, FreeBSD etc. ) GNS3 makes all of this emulation magic work together and allow you, for instance, to have your Cisco router talking to your Linux host. The possibilities are almost endless! GNS3 allows the emulation of Cisco IOSs on your Windows, Linux and Mac OS X based computer. Emulation is possible for a long list of router platforms and other devices.
Using an EtherSwitch card in a router, switching platforms may also be emulated to the degree of the card’s supported functionality. This means that GNS3 is an invaluable tool for preparing for Cisco certifications such as CCNA, CCNP and CCIE. There are a number of router simulators on the market, but they are limited to the commands that the developer chooses to include. Almost always there are commands or parameters that are not supported when working on a practice lab. In these simulators you are only seeing a representation of the output of a simulated router.
The accuracy of that representation is only as good as the developer makes it. With GNS3 you are running an actual Cisco IOS, so you will see exactly what the IOS produces and will have access to any command or parameter supported by the IOS. In addition, GNS3 is an open source, free program for you to use. However, due to licensing restrictions, you will have to provide your own Cisco IOSs to use with GNS3. Also, GNS3 will provide around 1,000 packets per second throughput in a virtual environment. A normal router will provide a hundred to a thousand times greater throughput.
GNS3 does not take the place of a real router, but is meant to be a tool for learning and testing in a lab environment. Using GNS3 in any other way would be considered improper. Quick Start Guide for Windows Users: Step 1 – Download GNS3 The easiest way to install GNS3 in a Windows environment is to download the all-in-one version. The file is a little under 16 MB in size and will take less than a minute to download on a DSL or cable connection. Dial-up connections will take somewhat longer. Step 2 – Install GNS3 Find the file you download and double-click on it to begin installing GNS3.
The GNS3 Setup Wizard will begin. Everything else is a matter of clicking on next or agree buttons. GNS3 depends on several other programs to operate. Those dependencies include WinPCAP, Dynamips and Qemu and these components along with GNS3 are all chosen by default for installation. The default location to install GNS3 is also chosen for you. Moreover note that if needed, WinPcap Setup Wizard will be launched for you to install it, this dependency is required for GNS3 to communicate with real networks through a physical network internal controller. The installation for WinPcap will begin.
However, if you have a previous version of WinPcap on your computer, the wizard will ask to remove the older version and will then install the newer version. You have now completed the installation of GNS3. Click the Start button, All Programs, GNS3, and then choose GNS3 out of the list of applications installed. You’ll see the main GNS3 window. We’ll discuss its panes in a later step, but first we have to configure the location for a Cisco IOS. Step 3 – Defining Cisco IOS files As mentioned earlier, you must provide your own Cisco IOS to use with GNS3 due to licensing issues.
GNS3 is meant to be used in a lab environment for testing and learning. Once you have obtained your own copy of a Cisco IOS for one of the supported platforms, you are ready to continue. Supported platforms are Cisco 7200, 3600 series (3620, 3640 and 3660), 3700 series (3725, 3745) and 2600 series (2610 to 2650XM, 2691). On the Edit menu, choose IOS image and hypervisors. Then under the IOS Images tab, click … and then find your Cisco IOS file and click Open. The file will appear as your Image file. Next, click the drop-down arrow next to Platform and choose the platform that corresponds to your IOS file.
Now click the drop-down arrow next to Model and choose the model corresponding to your IOS file. For now, we’ll accept the default values that remain. However, there is a very important value called the IDLE PC value that we will want to include. We’ll get to that later. Click the Save button and then the Close button. This will return you to the default GNS3 window. It’s time to create our very first simple topology. Creating the Simplest Topology: We describe how to build a more complex topology later, but for now, let’s just learn how to place one router on the desktop, start it, and console into it.
We will then learn how to find an idlepc value for the IOS we are using. This is a very important step. When an IOS is running, it will consume up to 100% of your CPU time. This will cause your computer to become very sluggish and will prevent building more complex topologies. However, if we use an idlepc value, we can reduce CPU usage dramatically. It puts the IOS into a sleep state when it is not in active use and wakes it up only when it is necessary. A more technical explanation will be given later. The GNS3 window is divided into four panes by default. The left-most pane lists the types of nodes available.
You will see router icons for the various platforms: PIX and ASA firewalls, Ethernet switch, ATM bridge, ATM switch, Frame Relay switch, Cloud, Qemu and VirtualBox guests etc. The right-most pane will provide a topology summary that will be better understood when we built more complex topologies. For now, just know that the pane exists. The middle section contains two panes. The top pane is your work area where a topology may be graphically built. The bottom pane, called the Console, shows Dynagen at work. Dynagen, as you recall, is the text-based front end to Dynamips, the core emulator being used.
Learning how to use Dynagen is like learning how to use DOS the first time, so we will not get into that here. However, we will use a very few simple but useful commands in the Dynagen pane. Configuring a router * Click on a router icon under Nodes Types corresponding to the IOS platform you are using. In our example, we are using a 3640 platform. You must use a platform for which you defined an IOS. Drag an appropriate router node type over to the workplace pane in the middle and let go. We now have a router ready to configure. Right-click the router and choose Configure. * Click on R1 and then the Slots tab.
Click the drop-down arrow next to slot0 and choose an adapter that includes FE in its description. This will add a FastEthernet adapter to the router. Next, click the drop-down arrow next to slot1 and choose PA-4T+, PA-4T, or NM-4T (if you do not have these exact adapters, just choose something close. ). This will add four serial interfaces to the router. Click OK. * Right-click the router and choose Start. Right-click the router again and choose Console. A Putty console opens up. * You may need to press Enter once initially in the Console window. After a few seconds, your virtual router should have started. * Apply an idlepc value Now it’s time to choose a idlepc value. Be sure you can see the prompt of your router in Putty window. Right-click R1 and choose Idle PC. GNS3 will spend a moment calculating an Idle PC value before presenting the screen to the right. If you click the drop-down arrow, you see a list of possible idlepc values. Potentially better idlepc values are marked with an asterisk. Choose one of the values with an asterick (in our example, we will choose number 1) and click OK. * If you choose IOS images and hypervisors on the Edit menu, and double-click on the image under the IOS Images tab, you’ll see the new idlepc value displayed under Settings.
You may repeat this process to find the value that reduces CPU usage the most, but this time use the Apply button so you can instantly see the effect of a idlepc value while observing the CPU usage. To observe CPU usage in Windows, press Ctrl+ALT+DEL and choose Task Manager. Click on the Performance tab to view CPU usage. In Ubuntu, choose System Monitor under Administration on the System menu. Click the Resources tab. You will observe that without an idlepc value, CPU usage will be at or near 100%, but with an idlepc value, CPU usage will drop to a very low value.