Day 3.2 - Designing/building a LAN

Introduction

In the last couple posts I went through setting up GNS3 to act a network simulator to route traffic between my virtual machines.

(As an aside, I had to update my Windows 2016 VM last night and it took... a really long time. At some point, the number of VMs I'm running may become an issue - especially with the number of routers I'm putting into the GNS3 VM. But I'll cross that bridge if I get there.)

LAN Design

I'm not a professional, so I didn't make this TOO terribly fancy. (Although it ended up being fancier than I originally anticipated.)

I had a few objectives:

• Multiple VLANs to practice trunking/switching/etc.
• A DMZ outside the main network
• A "core" network with multiple routes, to practice with routing protocols

With that in mind, here's what I came up with.

I made it in a program called CADE, which is a little finicky. I didn't want to start putting things into GNS3 - which makes them "real" - until I had a layout in mind.

As far as end-user devices go, GNS3 has a feature called VPCS - or, Virtual PC Simulator. This allows you to create miniature console-based VMs that do the bare minimum to respond to network traffic - so you can test connectivity from an end-user perspective, without going to the trouble of building a full-fledged OS-based VM.

With that in mind, for my virtual network, I decided I'm probably going to only run a single actual VM for testing Windows domain-based stuff, and use VPCS for the rest.

Starting the build

First thing to do: start GNS3 (which helpfully starts up its own VM.)

Next up: drag all my devices into place, and connect them.

Almost immediately I hit a snag: it turns out you can only have one device connected to a cloud interface. So I ended adding another router to the mix. At the end, it looked like this:

Next step was an IP addressing scheme. It's really complicated and not that exciting, so I'm going to skip it. Now for the fun part: going in and manually configuring all those routers.

Immediately, another problem emerges: the 2691 is a layer 2 switch. All the switching ports I used to set up the mesh can't be assigned IP addresses.

After some digging, I found that I should be using a Cisco 3745 router instead. Rather than using the 16-port switching plug-in, I just added a single extra virtual Ethernet port/card for each connection.

(Several hours later...)

Finally got it done.

With 7 out of 8 virtual routers running, as well as the Win2016 VM, my physical machine's barely using any CPU. (RAM is another story, but to be fair, I also have about 20 other programs open.)

Next step's going to be configuring all the routers to talk to each other... but that's for another day.