So let's create our first project in three.
At this point, we have a choice to make.
So whether we run three on the local server or within a virtual machine.
Because the primary reason for using Gns3 is simulating a network with switches and routers.
All we have to do is select the run only legacy iOS on my computer.
That's the option which is not selected by default.
So we leave this page with the rest of the default values.
It asks for the root permission for Oubridge to interact with a network interface.
So click yes to allow and enter the admin password.
Local server is started up and gns3 connected to it successfully.
So click next.
Finally, we have the summary of the project settings.
So click finish to end the project setup.
So as soon as you click, finish the new appliance template window appears.
So at this point, we're going to add an iOS router using a real iOS image.
So select the option and click okay.
So I'm assuming that you're a first time user of Gns3 and as such, you need to be aware that in order
to use this application software, at the minimum, you need to download one more piece of software.
So we already downloaded and installed the Gns3 software itself, which actually comes bundled with
a whole bunch of other stuff which isn't really needed.
And then you're also going to download at least one Cisco iOS software image.
I would suggest that you get hold of software images that support either the 3725 series router or the
3745 series router.
If you can get hold of these, that'll be the best.
So if you don't know anything about Cisco routers at all, you're just looking for some advice on which
particular one to choose for your iOS image.
I would select a 3007 25 or a 3745 image.
If you get software images for one, that's 3700 series of routers that comes along with like a switching
module.
You don't have to download anything else.
There's nothing that you have to do.
But basically you can turn on a switch that operates within or inside of that router, and then I can
do this switching and routing.
Most of the other platforms do not support that.
So in my particular case, I'm going to use a 3725 image.
And now I get to the point when we get to choose what iOS image we want to import into S3 And here is
where you get to browse for wherever you've downloaded the Cisco iOS software to.
I'm going to use a 3725 image, which I've already downloaded.
If you don't have it already, please search for the keywords such as Cisco, iOS 3725 Image download
and you'll find an image and then download it for yourself.
I'd love to show it to you, but I don't want to mess with legal issues.
It's not so hard, and I'm sure that you can easily find one.
Now, click Browse to select the iOS image.
So let me find my image.
Here it is.
Select it and click open.
And yes, I would like to decompress the image.
So click next.
Give a name.
Make it up whatever you want.
I'm going to choose C 3725.
That's pretty good for me.
So now before I leave the screen, there's also a little box here that says this is an ether switch
router, so you can just have every router in your topology as an ether switch.
I'm going to leave that unchecked for now.
We'll create a legacy router right now.
So make the default ram 256MB and then click next.
So here's where I get to select what modules or port adapters I want in my chassis.
It comes with a fast Ethernet slot already on it, and now I've selected in another slot so I can put
another fast Ethernet card and then I'll put another fast Ethernet card.
Why not?
So as I go forward, I've got some wick slots available.
Once again, these slots are available in the 3725.
Depending upon that software that you're using, you might not have all of these available to you.
So I'm going to put some serial interfaces in these slots.
So I'm going to have tons of interfaces in every single one of my routers to give me lots of flexibility
in the types of topologies that I want to design.
Don't worry.
I mean, we can change all these settings after the setup as well.
So now click next.
No, I don't want to waste time for the idle PC.
We can simply say that it's used to make the CPU usage much more effective.
So just click idle PC finder and let Gns3 find one for you.
And now we can hit finish.
And a router is available to us.
Now we can use it in our virtual topology.
All right.
So here are the preferences of three.
The router is added under the Dynamips iOS Routers menu.
You can see the menu on the tree at the left hand side of the window.
So click okay to close the preferences window.
Now is the time to name our first project.
As you can see here, the project location changes as well.
When you change the project name.
So click okay once you finished naming it.
And this is your main three window.
So now let's create another iOS router template and make it an either switch router.
This time around.
Now from the three main menu Select Preferences from the left hand Side Menu.
Select iOS Routers under the Dynamips Submenu and Click New.
We can use our existing image right now, so click next.
And I'd like to turn this router into a switch by selecting the ether switch box.
Let's go ahead and change the Ram to 256MB.
So now you can see it automatically populates one of those slots with a 16 port switch module.
And if you want, you can just leave it that way.
If the only thing that you're planning in the router is for 16 port ethernet switch.
But.
What I want to do is add more flexibility.
So I'm going to add some more slots just like the previous scenario.
Let the app find an idle PC.
And then click finish.
Now we have two different router templates.
The first one is a classic router and the second one is an ether switch router.
Now you can click edit to remove or add new slots, change a name, change a size, whatever you want
to do to customize it.