Your First Cisco GNS3 Topology
This document explains how to configure a simple GNS3 topology consisting of two Cisco routers. The set up shown here is the same when using either a local GNS3 installation or a GNS3 VM environment.
NOTEThis document assumes that you already have GNS3 installed and a Cisco IOS router image added to GNS3. If not, please refer to other guides which explain how to download, install and configure GNS3.
On first start up:
- When you first start GNS3, you will be prompted to create a new project:
- Name the project as desired and then click OK:
The following figure shows a screenshot of the GNS graphical user interface which we will quickly discuss so you know some of the terminology used:
The GNS3 workspace is the area of GNS3 where you create topologies by adding devices and links:
The GNS3 toolbar is found at the top of the GNS3 GUI and contains groups of icons that allow you to easily perform common tasks:
The toolbar groups icons into specific functions or features. This gives you a simple way of getting things done.
The devices toolbar allows you to add devices to your network topology. You do this by dragging devices from the Toolbar to the GNS3 workspace (explained below).
The devices toolbar is grouped into different types by default:
Add a link
You will find both simulated devices as well as emulated devices in the various device groupings.
- To create a new GNS3 topology, select a group of devices in the Devices Toolbar by clicking the device type button. In this example the Routers group was selected:
- The toolbar will expand to show available devices of that type. In this example a c3725 router is available to be used:
- Drag and drop the selected node (device) to the GNS3 Workspace. An instance of the node becomes available in the Workspace. In this example a router is now available:
- Drag and drop the node again into the GNS3 Workspace. In this example, another router was added to the GNS3 workspace:
- Click the Toolbar Device button again to collapse the group:
- Click the Add a Link button to start adding links to your topology. The mouse cursor will change to indicate that links can be added:
- Click on a device in your topology to display available interfaces. In this example various Fast Ethernet and Serial interfaces are available (this is device dependant):
- Click one of the interfaces and then select another device in the topology to connect the interface to. In this example FastEthernet 0/0 on R1 was selected and the link was joined to R2:
- Select an interface on the second device to complete the connection. In this example, FastEthernet 0/0 on R2 was selected:
- Click the Add a Link button to stop adding links. The mouse cursor will change back to normal to indicate that you have stopped adding links:
- Click the Show/Hide interface labels button on the GNS3 Toolbar to display interface labels in your topology:
- You are now ready to power on your network devices. Click the Start/Resume button on the GNS3 Toolbar to start up your network devices:
- GNS3 indicates that the devices have been powered on by turning the interface connectors from red to green. This can also be seen in the Topology Summary:
- You are now ready to configure your devices. Click the Console connect to all devices button on the GNS3 Toolbar to open a connection to every device in the topology:
- A console connection is opened to every device in the topology:
- In this example, the devices are configured as follows:
R1R1# configure terminal
R1(config)# interface fastEthernet 0/0
R1(config-if)# ip address 10.1.1.1 255.255.255.0
R1(config-if)# no shutdown
R2R2# configure terminal
R2(config)# interface fastEthernet 0/0
R2(config-if)# ip address 10.1.1.2 255.255.255.0
R2(config-if)# no shutdown
- R1 should now be able to ping R2:
R1# ping 10.1.1.2
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 10.1.1.2, timeout is 2 seconds:
Success rate is 80 percent (4/5), round-trip min/avg/max = 8/27/52 ms
- Now if you want to save your configuration on both router type:
R1# write memory
Congratulations! You have configured a basic GNS3 topology. From here on, you can create much more complex topologies and test and learn various technologies such as OSPF, EIGRP, BGP, STP and many others.