GNS3- A Brief User Guide

GNS3
A Brief User Guide
By
Zahra
Copyright © 2013 1Pv6. All Rights Reserved.

Understanding GNS
O GNS is a software that
allows us to work with
networks virtually
O It differs from “Packet
Tracer” in that it is less of
an illustrated simulation
and more of a genuine
virtual worktop
O This being the case- to
run it you need both
“GNS3” (can be
downloaded for free on
the internet) and Vmware
Workstation- a virtual
desktop software

Adding Devices
O Device Types on GNS
are listed in column
form on the left hand
side of the page
O To add a device to the
workspace:
- click the device type
e.g. switch
- choose the model you
want from the menu
- click and drag it to
your desired location

Configuring Devices:
Routers
O Configuration is required to add
interfaces to your routers
O To do this, simply right-click
your router and select
“configure”
O When the window appears,
select the router name on the
left (e.g. R2) and go to the
“slots” tab
O Unlike with Packet Tracer- the
available interface ports are not
illustrated visually- instead you
must remember the name of the
interface you wish to add and
select it from the drop down
menu
O Serial interfaces will require the
“WIC” section near the bottom

Configuring Devices:
End Devices/Hosts
O For this section you will
need “VMWare” and
its“Network Editor”
O GNS works by having the
machine you are working
on directly interact with
your simulated set up,
therefore if you wish to
have multiple end
devices in your topology,
they will need to be
virtual and consequently
require virtual network
cards and machines for
each device

Network Cards / NICs
O NIC stands for “Network
Interface Card”
O This is a small piece of
hardware installed into
a computer that allows it
to connect to a network
O “Network Editor” allows
for the creation of virtual
NICs so that virtual
devices are able to
connect

Creating a Virtual NIC
O To create a virtual
NIC for your end
device go to start and
find the program
“Network Editor”
O When it opens, click
“Add Network” and
then click “OK”
O You will need one for
each Host device in
your topology +1

Creating a Virtual Machine
O To create a virtual machine- open the
program “VMWare Workstation”, go
to file  new virtual machine
O A wizard will take you through the
next steps
O You will require an operating system
either from an external source e.g.
CD, USB OR an ISO file
O You won’t need to allocate much
RAM- go just above the
recommended, and don’t worry
about splitting disks
O Once created it will appear in the
column on the left
O To avoid going through the process
multiple times, when it is completed:
- Power off the machine by right
clicking it Power Power Off
- Then right click it again, Manage 
Clone.
A wizard will take you through the
next steps- make sure to make a
FULL clone.

Linking your GNS Hosts to
VMWare
O To link your Host to
VMware you first need to
assign virtual NICs to
each of your Hosts
O To do this- right click your
Host and select
“configure”
O Select your device in the
column on the left and a
page will appear with all
the NICs you have
created- delete them all
to leave your device
clean by selecting them
and hitting “delete”

VMWare (cont.)
O Finally, select the drop down
menu and select a virtual
NIC- these will be labelled
as “VMNet” followed by a
number
O Do not use VMNet 1 as it is
known to cause problems,
likely because it is reserved
O Start with VMNet2- select it
from the drop down menu
and click “ADD”
O Finalise the actions by
hitting “apply” followed by
“ok” at the bottom of the
window

VMWare (cont2.)
O Now enter VMWare
Workstation to connect your
virtual NIC to the Virtual
Machine (VM)
O Right click your VM and
select “settings”
O Select “Network Adapter”
and new options will appear
on the left
O Select the Virtual NIC from
the drop down menu and
click “ok” at the bottom of
the page
O These steps must be done
for each Host device

Powering on Devices
O To gain access to
command consoles etc.
the devices need to be
turned on
O In GNS, to turn on
singular device right-click
it and select “start”
O Alternatively, to power on
all devices click the
green button with the
“play” symbol on the tool
bar along the top of the
page
O In VMWare, right click
the virtual machine, go to
Power  Power On

Connecting Devices
O Provided that where need be
the correct interfaces have
been added- the next step is
to connect them
O Unlike with Packet Tracer,
there is no need for selecting
specific cabling
O Simply click the cable symbol,
click the first device and
select the desired interface,
then click the second device
you wish to connect to and
select the correct interface
there as well
O Finally click the cable symbol
again to cancel out of that
mode

Command Consoles
O Finally, with everything
configured, connected and
powered on- you will need
to access the command
consoles
O In GNS right click the
router and select “console”
O In Vmware, enter the VM
as if it were a desktop and
bring up the command
prompt from the start
menu- you will have to do
all pinging for that host
from within the VM

Configuring Host IP Addresses
O Each host will need an IP
address that has to be
configured from within the
VM
O To do this, enter each VM
individually, go to:
Start  Control Panel 
Network and Sharing Centre
O Then look under the
network and select “View
Status”
O Go to Properties  TCP/IP
Version 4  Properties
O Then simply type in your
desired IP, subnet and
default gateway
O “OK” to save settings and
close out

GNS3- A Brief User Guide

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