How to Install Cisco CML 2 Free on Proxmox VE (Step-by-Step Guide)
The Cisco Modeling Labs 2 (CML2) Free Edition is a powerful network simulation platform that allows you to build topologies of up to five nodes using Cisco IOL images. Although Cisco only supports CML on VMware, it can be installed on Proxmox with a few extra steps. This guide walks you through the entire process—from downloading the required files to importing the VM and enabling your free IOL nodes. Because Proxmox does not directly accept OVA uploads, we will also cover the correct manual method for converting and deploying the CML2 virtual machine.
📚 Table of Contents
- Requirements
- How to Download the Free CML2 OVA
- How to Download the Free IOL Refplat ISO
- How to Upload the CML2 Files to Proxmox
- How to Unpack the OVA in Proxmox
- How to Import the CML2 Disk into Proxmox
- How to Create the CML2 VM in Proxmox
- How to Attach the Refplat ISO for Free IOL Nodes
- First Boot and Initial Setup
- How to Enable the Free IOL Nodes
- CML Free Edition Limitations
1. Requirements
Before we begin, you will need the following:
- A running Proxmox VE server
- A Cisco.com (CCO) account — required to download CML2 Free Edition
- The CML2 Free Edition OVA file
- The refplat ISO containing free IOL node definitions and images
Although VMware is the officially supported hypervisor for CML2, Proxmox works once you manually convert the OVA. Furthermore, you will want nested virtualization enabled since CML uses KVM internally.
2. How to Download the Free CML2 OVA
To get started, visit the Cisco Modeling Labs Free Edition download page:
https://learningnetworkstore.cisco.com/cisco-modeling-labs-free
After logging in with your CCO ID, scroll until you see the CML2 Free OVA download link. Download the file named similar to:
cml2_f_2.x.x-x_amd64.ova
Since this is an OVA file, it bundles the .OVF and .VMDK files. However, Proxmox cannot upload OVA files through the GUI. Because of this, we will upload it manually and extract it on the server.
3. How to Download the Free IOL Refplat ISO
The free edition of CML2 includes access to Cisco IOL (IOS on Linux) routers and switches. However, you must download and mount the special refplat ISO to load the IOL nodes into your lab.
Download:
refplat-20250616-free-iso.zip
Unzip it locally and you will get a file similar to:
refplat-20250616-free.iso
This ISO contains:
- node-definitions (IOL routers & switches)
- virl-base-images (IOL OS images)
Later, we will mount this inside the CML VM so CML can import the free nodes.
4. How to Upload the CML2 Files to Proxmox
Now that you have your files, upload them to Proxmox. We will use the GUI as much as possible.
Upload the OVA (via SCP/GUI work-around)
Because the Proxmox GUI will not allow you to upload .ova files, you must upload it manually.
Option A – Use Proxmox GUI (rename trick)
Temporarily rename the file:
cml2.ova → cml2.ova.iso
Upload it into:
Datacenter → Storage (local) → ISO Images → Upload
Then SSH into Proxmox and rename it back:
mv /var/lib/vz/template/iso/cml2.ova.iso /var/lib/vz/template/iso/cml2.ova
Option B – Use SCP (recommended)
Upload directly into:
/var/lib/vz/template/iso/
With:
scp cml2_f_2.x.x.ova root@your-proxmox:/var/lib/vz/template/iso/
5. How to Unpack the OVA in Proxmox
Once the OVA is uploaded, extract it using tar:
cd /var/lib/vz/template/iso
tar -xvf cml2_f_2.x.x.ova
This will produce:
- cml2_xx.ovf
- cml2_xx-disk1.vmdk
- nvram and cert files
Now that the VMDK is extracted, we can import it into a Proxmox VM.
6. How to Import the CML2 Disk into Proxmox
Proxmox provides a command to import a VMware VMDK into a proper VM disk inside LVM-Thin.
Create a placeholder VM (we will edit it shortly):
In GUI:
Proxmox → Create VM
Use:
- VMID: 103 (or any free ID)
- Do not add a disk
- Use UEFI (OVMF)
- Machine type: q35
Then import the VMDK:
qm importdisk 103 cml2_xx-disk1.vmdk local-lvm
Next, attach the disk to the VM:
qm set 103 --scsi0 local-lvm:vm-103-disk-0
7. How to Create and Configure the CML2 VM
Open the VM in the Proxmox GUI and configure:
- BIOS: UEFI (OVMF)
- Machine: q35
- CPU Type: host
- Cores: 4–8 minimum
- Memory: 16GB minimum
- Network: VirtIO bridged to vmbr0
Important: CML requires an SMBIOS string. Add this in Proxmox Console:
qm set 103 --smbios1 "uuid=$(cat /proc/sys/kernel/random/uuid),manufacturer=Cisco,product=CML"
At this point, the VM should be ready to boot.
8. How to Attach the Refplat ISO for Free IOL Nodes
To enable Cisco IOL routers and switches, mount the refplat ISO:
In GUI:
VM 103 → Hardware → Add → CD/DVD Drive → Use ISO → refplat-2025.iso
Then inside the CML VM:
sudo mkdir /mnt/cdrom
sudo mount /dev/sr0 /mnt/cdrom
You should now see:
- /mnt/cdrom/node-definitions
- /mnt/cdrom/virl-base-images
CML automatically detects the files.
9. First Boot and Setup
Start the VM and proceed through the setup wizard. You will create:
- Admin user
- Management IP
- Initial lab directories
Once the web UI loads, log in at:
https://your-cml-IP
Next, we will enable the IOL node definitions.
10. How to Enable the Free IOL Nodes in CML
The free edition of CML cannot use IOSv or IOSvL2 images. You will only see IOL routers and switches. Therefore, importing the refplat ISO is mandatory.
To load the images:
CML UI → Tools → Node & Image Definitions
Scroll until you see:
- IOL L2 switch
- IOL L3 router
If they show as “available”, CML has detected the ISO properly.
Now you can start building 5-node topologies using IOL routers, switches, hubs, links, and Linux containers.
11. Free Edition Limitations
The free edition of CML includes the following restrictions:
- Maximum 5 nodes per topology
- IOL only (no IOSv, NX-OSv, XRv, etc.)
- No enterprise support
- No multi-user support
However, it is fully functional for CCNA, CCNP ENCOR, DMVPN, HSRP, VLANs, routing protocols, and switching labs.
Final Thoughts
Even though CML2 is designed for VMware, with the right steps it runs extremely well on Proxmox. By extracting the OVA, importing the VMDK, setting SMBIOS data, and loading the refplat ISO, you can enjoy a stable, free Cisco lab environment using only open-source virtualization. Moreover, once everything is installed, you can immediately begin creating DMVPN, HSRP, VLAN, and routing labs using the included IOL images.
