Once verified, the vqfx202r110reqemuqcow2 will outperform many older vQFX images, offering stable EVPN and MPLS data plane forwarding. Happy virtual networking!

This article is part of a series on open-source network emulation. For further reading, explore Juniper’s official vQFX documentation or the libvirt user guide.

Running the vQFX-20.2R1.10 virtual routing engine (vqfx-20.2R1.10-re-qemu.qcow2) requires a dual-VM setup because the vQFX is split into a Routing Engine (RE) and a Packet Forwarding Engine (PFE). To make it work, you must link these two separate QEMU virtual machines over a dedicated internal network. Core Components Required To get a functional switch, you need both images: RE Image: vqfx-20.2R1.10-re-qemu.qcow2 (the control plane).

PFE Image: Typically vqfx-20.2R1-2019010209-pfe-qemu.qcow (the data plane). Step-by-Step Configuration

The following specifications are standard for platforms like GNS3 or EVE-NG: 1. VM Resource Allocation vCPUs: Assign 2 vCPUs to each VM.

RAM: Allocate at least 1024 MB for the RE and 2048 MB to 4096 MB for the PFE.

NIC Type: Crucially, set the network interface type to virtio-net-pci; otherwise, the RE and PFE may fail to communicate. 2. Critical Interface Wiring You must connect the VMs precisely for them to "handshake":

RE Interface em0: Reserved for Management/Out-of-Band access.

RE Interface em1: Must connect directly to PFE Interface em1. This is the internal control link between the brain (RE) and the muscle (PFE).

RE Interface em2 and above: These are your actual switch ports (e.g., xe-0/0/0) where you connect other network devices in your lab. 3. Initial Access Default Username: root. Default Password: Juniper (case-sensitive). Known Issues & Troubleshooting

Version Mismatch: Although the filename says 20.2, some users report the image actually runs version 19.4R1.

Boot Time: The vQFX is notoriously slow to boot. It can take 7 to 10 minutes for the interfaces to fully populate and the RE to become "Master".

Graceful Shutdown: Always use request system power-off both-routing-engines to avoid disk corruption or "non-master" role issues on the next boot. Guide: Importing Juniper vMX and vQFX into CML2.4

. This image is designed to run in a QEMU/KVM environment, often within network simulation platforms like

To get this specific image working, you typically need its counterpart, the PFE (Packet Forwarding Engine)

image, as the vQFX architecture splits these functions into two separate virtual machines. How to Get vQFX 20.2R1.10 Working

To successfully boot and use this image, follow these integration steps: Pair with the PFE : A vQFX setup requires two nodes. While your file is the RE (Control Plane) , you also need the corresponding vqfx-20.2R1.10-pfe-qemu.qcow2 Data Plane ) for traffic to actually flow. Resource Allocation RE (Your file) : Assign at least : Assign at least Connectivity : In your simulator (like EVE-NG), you must connect the interface of the RE to the

interface of the PFE. This internal link allows the "brain" (RE) to talk to the "muscle" (PFE). Management Access interface on the RE for SSH/Telnet management. Virtualization Settings Nested Virtualization

(VT-x/AMD-V) is enabled on your host machine, as Junos OS runs as a VM within QEMU. Common Troubleshooting Stuck at Boot

: If the RE hangs at the login prompt or doesn't see interfaces, ensure the PFE is powered on and the internal link is correctly mapped. License Warnings

: vQFX usually comes with a trial period. For lab use, "Evaluation" mode is standard, though some advanced features may require a license. QEMU Version QEMU 2.4.0 or higher for the best stability with Junos 20.x images.

It sounds like you're working with VQFX (virtual Juniper vQFX), specifically a file named something like vqfx202r110reqemuqcow2 — likely a QEMU QCOW2 image for a vQFX switch (vQFX 20.2R1.10?).

Since you asked to "develop a feature" on this, I’ll assume you want to extend, automate, or enhance the behavior of a vQFX instance running from that QCOW2 image under KVM/QEMU.

Below is a structured plan to develop a custom feature — for example, adding automated config deployment + telemetry export to this vQFX switch.

After defining the VM, start it:

virsh start vqfx-re
virsh console vqfx-re

You should see the FreeBSD boot loader. Patience is critical—the first boot can take 3-5 minutes as it expands the root filesystem.

If you see a kernel panic referencing virtio_blk or pci_alloc, your XML is incorrect. Return to Step 2 and verify the machine type.

For traffic forwarding tests (e.g., VXLAN routing), the RE alone won’t work. You need a separate vQFX PFE image (vqfx202r110pfe.qcow2). Connect them via a virtual back-to-back link using a socket or vhost-user interface.

Simplify by using Juniper vLab or containerlab with the following topology:

name: vqfx-evpn-lab
topology:
  nodes:
    spine:
      kind: juniper_vqfx
      image: vqfx202r110re-qemu.qcow2
      startup-config: spine.cfg
    leaf1:
      kind: juniper_vqfx
      image: vqfx202r110re-qemu.qcow2
  links:
    - endpoints: ["spine:ge-0/0/0", "leaf1:ge-0/0/0"]

Vqfx202r110reqemuqcow2 Work -