Run Cisco CML 2.9.x on KVM (virt-manager)

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Cisco Modeling Labs (CML) is an awesome way to practice routing/switching labs without owning physical gear. The catch: Cisco primarily distributes CML as an OVA (Open Virtual Appliance), which is most commonly used with VMware products.

If you’re on Linux and prefer KVM/libvirt (or you just don’t want to use VMware), you’re not stuck. This guide walks through the full process of running Cisco CML 2.9.x on KVM using virt-manager, including importing the refplat image bundle so you can actually add routers and switches in your labs.

What you’ll achieve

By the end, you’ll have:

  • A working CML controller VM running on KVM

  • Access to:

    • CML Web UI (where you build labs)

    • Cockpit (system admin/maintenance)

  • refplat imported, so you can add router/switch nodes like IOSv and IOSvL2

About the CML Free Version (the one I’m using)

For this setup I’m using the CML free/personal release. It’s perfect for learning and building small labs, but it has limits compared to a paid license.

The biggest one:

  • Maximum 5 running nodes at a time

That’s still great for lots of CCNA/CCNP practice, like:

  • 2 routers + 1 switch + 2 endpoints = 5 nodes

  • Larger enterprise topologies = you’ll hit the cap (upgrade later if you need)

Tip: With a 5-node limit, build labs around one concept at a time (routing-only, switching-only, etc.) and keep topologies tight.

Requirements

Hardware (recommended)

  • 4+ CPU cores

  • 8–16 GB RAM (16 GB makes labs smoother)

  • Virtualization enabled in BIOS/UEFI (Intel VT-x / AMD-V)

Host packages

You need KVM + libvirt + virt-manager + qemu tools.

Fedora:

sudo dnf install -y @virtualization virt-manager qemu-img
sudo systemctl enable --now libvirtd

Ubuntu/Debian:

sudo apt update
sudo apt install -y qemu-kvm libvirt-daemon-system virt-manager qemu-utils
sudo systemctl enable --now libvirtd

(Optional but recommended)

sudo usermod -aG libvirt,kvm $USER
# log out and log back in

Files you need

  1. CML Controller OVA (example: cml2_f_2.9.1-7_amd64-7.ova)

  2. refplat ISO (example: refplat-20250616-free.iso)

  3. Enough disk space (CML + images can be large)

Note: Use images you’re entitled to download and run.

Step 1 — Extract the OVA

The OVA is basically a tar archive. Extract it like this:

cd ~/Downloads
tar -xvf cml2_f_2.9.1-7_amd64-7.ova

After extracting, you should see files like:

  • ... .ovf

  • ... -disk1.vmdk

  • ... .nvram

Step 2 — Convert the VMDK to QCOW2

KVM works best with QCOW2, so convert the VMware disk:

cd ~/Downloads
qemu-img convert -O qcow2 \
  cml2_2.9.1-7_amd64-7_SHA256-disk1.vmdk \
  cml2-controller.qcow2

Move it into libvirt’s images directory:

sudo mv cml2-controller.qcow2 /var/lib/libvirt/images/

Step 3 — Create the VM in virt-manager

Open virt-manager → New VM:

  • Choose: Import existing disk image

  • Disk: /var/lib/libvirt/images/cml2-controller.qcow2

Recommended VM settings:

  • Chipset / Machine type: Q35

  • Firmware: UEFI (Secure Boot OFF if you have that option)

  • Disk bus: VirtIO

  • NIC model: VirtIO

  • CPU/RAM: at least 4 vCPU / 8 GB RAM

Step 4 — Attach refplat ISO as a SATA CD-ROM

The refplat bundle is what provides the images/templates for routers and switches.

In virt-manager:

  • VM settings → Add Hardware

  • Storage → CDROM

  • Select your refplat ISO

  • Set Bus to: SATA

  • Enable: Connect at power on

Boot order (important)

Go to Boot Options and set:

  1. VirtIO Disk

  2. SATA CDROM

Step 5 — Boot and find the CML IP address

Start the VM.

If the VM console doesn’t clearly show the IP, run this on the host:

sudo virsh net-dhcp-leases default

You’ll get an IP like:
 192.168.122.xx

Step 6 — admin vs sysadmin (important)

CML has two “worlds” and people often mix these up:

CML Web UI (build labs)

  • URL: https://<CML-IP>/

  • Login: admin (CML UI account)

Cockpit (system maintenance)

  • URL: https://<CML-IP>:9090/

  • Login: sysadmin (system account)

Also:

  • The VM console login (cml-controller login:) uses sysadmin credentials.

Step 7 — Import/copy refplat images into CML

Newer CML versions copy the refplat content from the ISO into local disk.

If it copies automatically

Sometimes you’ll see a message like:

“refplat has been copied and can be removed.”

If you see that, you’re likely done.

If you need to copy it manually

Open Cockpit:
 https://<CML-IP>:9090/ → login sysadmin

Then run:

  • Copy Refplat ISO to Disk

If Cockpit times out

From console/SSH:

sudo /usr/share/cockpit/virl2/copy-refplat-iso-to-disk.sh &

Step 8 — Verify router/switch nodes are available

In CML Web UI:

  • Create a new lab → Add node

You should see options like:

  • IOSv (router)

  • IOSvL2 (switch)

If you can add them and start them, you’re ready to build labs.

Step 9 — Remove the refplat ISO (cleanup)

Once refplat is imported:

  • virt-manager → CDROM → Disconnect / Remove media

  • Keep boot order with the disk first

Quick mapping: which image is router vs switch vs firewall?

Router

  • IOSv → general routing practice (OSPF/EIGRP/BGP labs)

Switch

  • IOSvL2 → VLANs, trunking, STP, EtherChannel

Firewall

Firewalls may not be included in your free refplat bundle. If you have access:

  • ASAv → simplest firewall to start with

  • FTDv → NGFW (more complex, often managed with FMC)

Common issues / troubleshooting

No IP / can’t access UI

  • Ensure VM NIC is connected to libvirt “default” network

  • Check DHCP leases:

sudo virsh net-dhcp-leases default

Nodes won’t start / unstable performance

  • Increase RAM/CPU

  • In virt-manager, set CPU model to host-passthrough if available

  • Confirm virtualization is enabled in BIOS

UEFI option missing / firmware issues

If your distro doesn’t have UEFI firmware packages installed:

Fedora:

sudo dnf install -y edk2-ovmf
sudo systemctl restart libvirtd

Ubuntu:

sudo apt install -y ovmf
sudo systemctl restart libvirtd

Done!

Now you can build small-but-realistic labs (perfect for the CML free 5-node limit), like:

  • Router-to-router OSPF

  • VLAN + trunking + STP

  • Routing + ACL basics

If you’re studying CCNP, you can still do a lot with 5 nodes—just keep your topology tight and focus on one concept per lab.


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