Part 1 of the GNS3 Lab Build: Building the Proxmox Server
I really like the idea of being able to break a network from anywhere.
Not a real network, obviously. Apparently that’s frowned upon.
But a virtual one? Perfectly acceptable. In fact, some might even say educational.
That’s the main reason I wanted to make my own dedicated GNS3 server. I don’t like the idea of having my labs trapped on whatever device I happen to be using that day. Sometimes I’m on my desktop. Sometimes I’m on my laptop. And sometimes I want to connect through my VPN and poke at something while I’m not even at home.
If the lab lives on my desktop, then it’s only accessible when I’m sitting at my desktop.
But with a dedicated server, I can access it whenever I want.
So GNS3 needed its own home.
A few months earlier, I had bought a Dell Optiplex 7050 small form factor (SFF). For only £60, I got a pretty decent machine:
- Intel® Core™ i5-7500, 4 cores, 4 threads @ 3.40 GHz, boost up to 3.80 GHz
- 16 GB DDR4 RAM
- 256 GB SATA SSD
Honestly, I was already really happy with that. I’ve seen individual 16 GB RAM kits listed online for over £40, so getting the machine for £60 felt like a bargain.
Of course, knowing me, it didn’t stay a £60 machine for long.
The Upgrades
The Optiplex came with a 256 GB SATA SSD and a CD-ROM drive.
I honestly can’t remember the last time I actually used a CD drive, but I think it was around ten years ago, burning questionably sourced episodes of Family Guy to watch on a portable DVD player at summer camp.
Anyway, the CD-ROM had to go.
I had a CD-ROM-to-2.5” SATA bay adapter lying around from an old rack server I had upgraded, so I moved the original SSD into this bay. That freed up the main drive bay for something bigger.
The plan was simple: add more storage.
And before you ask why, I’m not too sure myself. I’m sure 256 GB would’ve been enough to get started, but I also don’t want to worry about storage in the future.
I ordered a used 1 TB 3.5” hard drive from eBay for £17.20 along with a drive caddy for £5.99 so I could properly mount it inside the case.
There was just one tiny issue.
I bought a caddy for a Dell Optiplex 7050. Not a Dell Optiplex 7050 SFF.
You know when people say the square peg goes in the square hole?
Well, imagine my surprise when the square peg arrived and it was approximately twice the size of the square hole.
Technically I had bought the right part, just for the wrong computer. The listing said 7050, the computer said 7050, and my brain decided there was no need to double-check anything on this occasion.
Maybe I should have double-checked.
So the 1 TB drive was temporarily attached with… drum roll please… Velcro tape.
Because apparently every LabForger project has to involve Velcro tape at some point.
While I had the machine open, I also decided to repaste the CPU.
I have no idea if it had been done since leaving the factory, but when I lifted the heatsink, it looked more like cement than paste. Luckily I already had some paste lying around so I cleaned off the old stuff and applied a fresh layer.
I also got a bit carried away.
As soon as I saw the empty PCIe slots, my brain started thinking of all the ways I could fill them under the excuse of “future proofing.”
Eventually, I settled on an Intel I350-T4 four-port NIC.
Did I need four extra Ethernet ports immediately? No.
Did that stop me from doing it? Also no.
The Software
When I originally bought this device, I was in the middle of getting rid of my old Dell servers because you could literally hear them from the other side of my apartment.
This created a small problem.
I still needed somewhere to run my self-hosted services, but I no longer wanted to wake up to the sound of a small jet engine preparing for take-off. The original plan was to install Proxmox and use the Optiplex as a general-purpose homelab server.
That way, instead of dedicating the entire machine to one thing, I could split it into different virtual machines and give each service its own little place to live.
Then I did absolutely nothing with it for over three months.
At that point, I started to wonder if all those self-hosting plans were actually as urgent as I had originally told myself. Since the main thing I wanted was a GNS3 server, I considered skipping Proxmox entirely and just installing Ubuntu Server with GNS3 on top.
Of course, that option was too easy, so back to Proxmox I went.
Lately, I’ve been thinking it would be useful to have a Grafana dashboard for monitoring, NetBox for IP address management, and maybe some other services later on. Even if GNS3 is the main reason I finally got round to this project, I like knowing I can expand without having to rebuild the server later.
If I’m going to use this Optiplex as the main server for the LabForger homelab, then I might as well future-proof it, even just a little bit.
The main thing that put me off was nested virtualisation.
I was worried that running virtual devices inside GNS3, inside a VM, inside Proxmox would kill performance on a machine that’s already not exactly top of the line. In my head, the setup looked something like this:
Proxmox PVE
├── GNS3 Server
│ ├── Cisco IOS
│ ├── MikroTik Cloud Hosted Router (CHR)
│ ├── OPNsense
│ ├── Windows & Linux VMs
│ └── ...
└── Other VMs
└── ...In my head, it looked like I was planning a disaster and I would be regretting it all in a matter of days.
After doing some research on nested virtualisation, I found this Proxmox wiki article explaining that the VM’s CPU type can be set to host. My understanding is that this lets the GNS3 VM use more of the real CPU features from the Optiplex, including the virtualisation support needed for KVM.
This was the important part for me. I didn’t want to put GNS3 inside Proxmox if it meant creating performance problems before I’d even started building labs.
The article also says you can check whether nested virtualisation is enabled from the Proxmox shell:
root@pve01:~# cat /sys/module/kvm_intel/parameters/nested
YSeeing that Y gave me a bit more confidence that I was on the right track.
So the final plan was set: Proxmox on the Optiplex, with GNS3 running inside its own VM.
Installing Proxmox
With the hardware sorted and the plan established, it was time to actually install Proxmox.
The install itself was really simple. I grabbed my Ventoy USB, which already had Proxmox on it, booted the Optiplex from it, selected the install disk, configured the network, set the hostname, and created a root password using my password manager.
Then I went to log in and realised the password was not actually in my password manager.
Turns out, I’d generated the password and then forgotten to press save.
Since this was a completely fresh install, I decided to just reinstall the whole operating system.
Of course I would find a way to make even the simplest task more… interesting.
The second attempt went much better. This time, I made sure the password was actually saved before finishing the install, then logged into the Proxmox web interface from my desktop.
I also took the opportunity to add a DHCP reservation and create another local DNS record for pve01.home.labforger.com.
And just like that, the £60 Optiplex was no longer just an old office PC. It was the first proper server in my LabForger homelab.
Was It Worth It?
Yes.
On its own, all I really did was upgrade an old office computer and install an operating system on it. Not exactly groundbreaking.
However, this machine is the foundation for a lot of what I want to build next. Before building everything else on top of it, I think it was worth taking the time to explore my options, both hardware and software, so I could make better decisions for what I actually want this server to do.
Knowing me, that doesn’t mean everything is going to be seamless.
But hopefully there’ll be fewer bumps along the road.
GNS3 is still the main reason this machine exists, but it definitely won’t be the only thing I use it for. Now that Proxmox is set up, I’ve got the freedom to add whatever else I need later, whether that’s monitoring, dashboards, IPAM, or literally anything else I convince myself is essential.
Next step?
Setting up the GNS3 server.