How to Convert Cisco .bin Files to .qcow2 for Virtual Labs If you are building a network lab in GNS3, EVE-NG, or PNETLab, you’ve likely encountered Cisco IOS images ending in .bin. While these files work perfectly on physical hardware, modern network simulators perform best with .qcow2 (QEMU Copy-On-Write) files.
Converting these images allows you to run Cisco routers and switches as lightweight virtual machines, enabling features like snapshots and better resource management. Understanding the File Formats
BIN (.bin): A binary executable file designed to run directly on Cisco hardware (ASICs and processors).
QCOW2 (.qcow2): A virtual disk format used by QEMU. It is "sparse," meaning it only uses physical disk space as data is written to the virtual drive, making it ideal for large-scale lab environments. Prerequisites
Before starting, ensure you have the following installed on your Linux machine or WSL (Windows Subsystem for Linux): QEMU Utilities: This provides the qemu-img tool.
Cisco IOS Image: A valid .bin file (e.g., c7200-adventerprisek9-mz.152-4.M1.bin). To install the necessary tools on Ubuntu/Debian, run: sudo apt-get update sudo apt-get install qemu-utils Use code with caution. Step-by-Step Conversion Process 1. Extracting the Image (If Necessary)
Some Cisco .bin files are compressed. While you can often convert them directly, certain older platforms require you to extract the actual IOS runtime from the loader. However, for most modern GNS3/EVE-NG setups, we focus on wrapping the bootable image into a virtual disk. 2. Create a Raw Image
First, we create a raw disk image that matches the size requirements of the IOS software. Most standard IOS images fit within a 512MB or 1GB disk. qemu-img create -f raw flash.raw 512M Use code with caution. 3. Convert the BIN to QCOW2 convert cisco bin to qcow2
The most common "conversion" isn't actually changing the code inside the BIN, but rather converting a disk image containing the BIN into a QCOW2 format that a hypervisor can read.
However, if you are using Cisco VIRL/CML images (which often come as .vmdk or .iso), the command to move directly to .qcow2 is:
qemu-img convert -f vmdk source_image.vmdk -O qcow2 destination_image.qcow2 Use code with caution. 4. The "Manual" Wrap for Physical BINs
For traditional IOS images (like those for a 7200 router), you don't typically "convert" the file. Instead, you define the .bin as the boot localized file within your emulator's settings.
If you are working with Cisco ASA or ASAv, you might need to convert a disk image:
Rename your bin to a disk format if it's a bootable disk image. qemu-img convert -O qcow2 input_file.bin output_file.qcow2 Use code with caution. Integrating into Your Lab
Once you have your .qcow2 file, follow these steps to use it: How to Convert Cisco
EVE-NG: Upload the file to /opt/unetlab/addons/qemu/ inside a folder named after the device (e.g., asav-9.15.1/). Rename the file to virtioa.qcow2.
GNS3: Use the "New Template" wizard, select "Manual Import," and point the QEMU binary to your newly created .qcow2 file. Optimization Tips
Compression: Use the -c flag during conversion to shrink the file size further:qemu-img convert -c -O qcow2 input.bin output.qcow2
Idle-PC Values: If you are running converted images in GNS3, remember to calculate an Idle-PC value to prevent the virtual router from consuming 100% of your host CPU.
By converting your Cisco images to .qcow2, you ensure maximum compatibility with KVM-based simulators and gain the ability to scale your network labs without crashing your host system.
Before attempting conversion, you must understand what these files actually contain.
The first step is to extract the contents of the BIN file. You can use the dd command to skip the header and extract the raw firmware image: This command skips the first 512 bytes of
dd if=cisco_ios.bin of=cisco_ios.raw bs=1 skip=512
This command skips the first 512 bytes of the BIN file (which contains the header) and extracts the raw firmware image into a new file called cisco_ios.raw.
| Cisco Platform | QCOW2 Conversion Support | Notes |
|----------------|--------------------------|-------|
| CSR1000v (IOS-XE) | ✅ Full | Boot via kernel or bootloader |
| ASAv (ASA on KVM) | ✅ Full | Requires specific OVA → qcow2 extraction |
| vIOS / vIOS-L2 | ✅ Native | Already qcow2 in VIRL/CML packages |
| IOS (7200, 3725) | ⚠️ Partial | Better as -kernel boot, not disk-based |
| NX-OS (Titanium) | ❌ Not supported | Uses different boot architecture |
Next, you'll use the qemu-img command to convert the raw firmware image to Qcow2 format:
qemu-img convert -f raw -O qcow2 cisco_ios.raw cisco_ios.qcow2
This command converts the cisco_ios.raw file to Qcow2 format and saves it as cisco_ios.qcow2.
Install GRUB to the raw disk:
grub-install --target=i386-pc --boot-directory=/mnt/cisco/boot /dev/loop0
Ensure GRUB stage files are present; you may need to install
grub-pc-binon Debian/Ubuntu.
sudo umount /mnt sudo qemu-nbd -d /dev/nbd0
QCow2 (QEMU Copy On Write version 2) is a disk image format used by QEMU. It supports sparse storage, snapshots, and compression. For an emulator to boot a Cisco image, it requires a disk structure (like a virtual hard drive) containing a bootable partition with the extracted IOS filesystem.