KVM Multiple Devices Testbed Setup

March 30, 2026 · View on GitHub

This document describes the steps to setup a virtual switch based testbed, deploy a multiple devices and multiple protocols topology to it, and run a quick test to verify it is working as expected.

Prepare testbed host

First, we need to prepare the host where we will be configuring the virtual testbed and running the tests.

Install Ubuntu AMD64 on your host or VM
- To setup a multiple devices topology, the server needs to have at least 20GB (96GB if you deploy multiple cisco devices topology) of memory free
- If the testbed host is a VM, then it must support nested virtualization
  - Instructions for Hyper-V based VMs
Prepare your environment based on Ubuntu 20.04, make sure that python and pip are installed sudo apt install python3 python3-pip openssh-server If the server was upgraded from Ubuntu 18.04, check the default python version using command python --version. If the default python version is still 2.x, replace it with python3 using symbolic link: sudo ln -sf /usr/bin/python3 /usr/bin/python

Run the host setup script to install required packages and initialize the management bridge network

git clone https://github.com/sonic-net/sonic-mgmt
cd sonic-mgmt/ansible
sudo -H ./setup-management-network.sh

Install Docker CE. Be sure to follow the post-install instructions so that you don't need sudo privileges to run docker commands.

We currently support IOS-XR-based, EOS-based or SONiC VMs to simulate neighboring devices in the virtual testbed, much like we do for physical testbeds. To do so, we need to download the image to our testbed host.

Option 1: cEOS (container-based) image (recommended)

Prepare folder for image files on test server

Create a subfolder called images inside the root_path directory defined in ansible/group_vars/vm_host/main.yml file. For instance, if root_path is set to veos-vm, you should run the following command:
```
mkdir -p ~/veos-vm/images
```
Prepare the cEOS image file

Option 1.1: Manually download cEOS image
1. Obtain the cEOS image from Arista's software download page.
2. Place the image file in the images subfolder located within the directory specified by the root_path variable in the ansible/group_vars/vm_host/main.yml file.
  
  Assuming you set root_path to veos-vm, you should run the following command:
```
cp cEOS64-lab-4.29.3M.tar ~/veos-vm/images/
```
  The Ansible playbook for deploying testbed topology will automatically use the manually prepared image file from this location.
Option 1.2: Host the cEOS image file on a HTTP server

If you need to deploy VS setup on multiple testbed hosts, this option is more recommended.
1. Download the cEOS Image
  
  Obtain the cEOS image from Arista's software download page.
2. Host the cEOS Image
  
  Host the cEOS image file on an HTTP server. Ensure that the image file is accessible via HTTP from the sonic-mgmt container running the testbed deployment code. For example, the URL might look like http://192.168.1.10/cEOS64-lab-4.29.3M.tar.
3. Update the Ansible Configuration
  
  Update the ceos_image_url variable in ansible/group_vars/vm_host/ceos.yml with the URL of the cEOS image. This variable can be a single string for one URL or a list of strings for multiple URLs.
  
  The Ansible playbook will attempt to download the image from each URL in the list until it succeeds. Downloaded file is stored to images subfolder of the location determined by root_path variable in ansible/group_vars/vm_host/main.yml. For example if root_path is /data/veos-vm, then the downloaded image file is put to /data/veso-vm/images
  
  Variable skip_ceos_image_downloading in ansible/group_vars/vm_host/ceos.yml also must be set to false if you wish ansible playbook to automatically try downloading cEOS image file. For example
```
ceos_image_url: http://192.168.1.10/cEOS64-lab-4.29.3M.tar
skip_ceos_image_downloading: false
```
  Or:
```
ceos_image_url:
   - http://192.168.1.10/cEOS64-lab-4.29.3M.tar
skip_ceos_image_downloading: false
```

Note When downloading, the version specified above might be outdated or unavailable. Please check the Arista recommended release to obtain the latest recommended image and import it into your local Docker registry. The actual image version that is needed in the installation process is defined in the file ansible/group_vars/vm_host/ceos.yml, make sure you modify locally to keep it up with the image version you imported.*

Note: Please be aware of the image's CPU architecture (32 vs 64-bit). In the example above, it is a standard 64-bit cEOS image. Ensure you import the correct image according to your requirements.

Option 2: Use Cisco image as neighboring devices

You need to prepare a Cisco IOS-XR image cisco-vs.img in ~/veos-vm/images/.The actual image version that is needed in the installation process is defined in the file ansible/group_vars/vm_host/main.yml:cisco_image_filename. We don't support to download cisco image automatically, you can download an available image from Download Cisco image and put it into the directory ~/veos-vm/images

Download the sonic-vs image

To run the tests with a virtual SONiC device, we need a virtual SONiC image. The simplest way to do so is to download the latest succesful build.

Download the sonic-vs image from here

wget "https://sonic-build.azurewebsites.net/api/sonic/artifacts?branchName=master&platform=vs&target=target/sonic-vs.img.gz" -O sonic-vs.img.gz

Unzip the image and copy it into ~/sonic-vm/images/ and also ~/veos-vm/images

gzip -d sonic-vs.img.gz
mkdir -p ~/sonic-vm/images
cp sonic-vs.img ~/sonic-vm/images
mv sonic-vs.img ~/veos-vm/images

Setup sonic-mgmt docker

All testbed configuration steps and tests are run from a sonic-mgmt docker container. This container has all the necessary packages and tools for SONiC testing so that test behavior is consistent between different developers and lab setups.

Run the setup-container.sh in the root directory of the sonic-mgmt repository:
```
cd sonic-mgmt
./setup-container.sh -n <container name> -d /data
```
From now on, all steps are running inside the sonic-mgmt docker, unless otherwise specified.

You can enter your sonic-mgmt container with the following command:

docker exec --user $USER -it <container name> bash

You will find your sonic-mgmt directory mounted at /data/sonic-mgmt:

$ ls /data/sonic-mgmt/
LICENSE  README.md  __pycache__  ansible  docs	lgtm.yml  setup-container.sh  spytest  test_reporting  tests

Setup host public key in sonic-mgmt docker

In order to configure the testbed on your host automatically, Ansible needs to be able to SSH into it without a password prompt. The setup-container script from the previous step will setup all the necessary SSH keys for you, but there are a few more modifications needed to make Ansible work:

Modify /data/sonic-mgmt/ansible/veos_vtb to use the user name (e.g. foo) you want to use to login to the host machine (this can be your username on the host)

foo@sonic:/data/sonic-mgmt/ansible$ git diff
diff --git a/ansible/veos_vtb b/ansible/veos_vtb
index 3e7b3c4e..edabfc40 100644
--- a/ansible/veos_vtb
+++ b/ansible/veos_vtb
@@ -258,7 +258,7 @@ vm_host_1:
     STR-ACS-VSERV-01:
       ansible_host: 172.17.0.1
       ansible_user: use_own_value
-      vm_host_user: use_own_value
+      vm_host_user: foo

vms_1:
   hosts:

Create a dummy password.txt file under /data/sonic-mgmt/ansible
- Note: Here, password.txt is the Ansible Vault password file. Ansible allows users to use Ansible Vault to encrypt password files.
  
  By default, the testbed scripts require a password file. If you are not using Ansible Vault, you can create a file with a dummy password (e.g. abc) and pass the filename to the command line. The file name and location is created and maintained by the user.
On the host, run sudo visudo and add the following line at the end:
```
foo ALL=(ALL) NOPASSWD:ALL
```
Verify that you can login into the host (e.g. ssh foo@172.17.0.1, if the default docker bridge IP is 172.18.0.1/16, follow https://docs.docker.com/network/bridge/#configure-the-default-bridge-network to change it to 172.17.0.1/16, delete the current sonic-mgmt docker using command docker rm -f <sonic-mgmt_container_name>, then start over from step 1 of section Setup sonic-mgmt docker ) from the sonic-mgmt container without any password prompt.
Verify that you can use sudo without a password prompt inside the host (e.g. sudo bash).

Deploy multiple devices topology

Now we're finally ready to deploy the topology for our testbed! Run the following command:

(Optional) The connectivity to the public internet is necessary during the setup, if the lab env of your organization requires http/https proxy server to reach out to the internet, you need to configure to use the proxy server. It will automatically be leveraged on required steps (e.g. Docker daemon config for image pulling, APT configuration for installing packages). You can configure it in ansible/group_vars/all/env.yml

cEOS

cd /data/sonic-mgmt/ansible
./testbed-cli.sh -t vtestbed.yaml -m veos_vtb -k ceos add-topo vms-kvm-wan-pub password.txt

Verify that the cEOS neighbors were created properly:

$ docker ps
CONTAINER ID        IMAGE                                                 COMMAND                  CREATED              STATUS              PORTS               NAMES
575064498cbc        ceosimage:4.23.2F                                     "/sbin/init systemd.…"   About a minute ago   Up About a minute                       ceos_vms6-1_VM0103
d71b8970bcbb        debian:jessie                                         "bash"                   About a minute ago   Up About a minute                       net_vms6-1_VM0103
3d2e5ecdd472        ceosimage:4.23.2F                                     "/sbin/init systemd.…"   About a minute ago   Up About a minute                       ceos_vms6-1_VM0102
28d64c74fa54        debian:jessie                                         "bash"                   About a minute ago   Up About a minute                       net_vms6-1_VM0102
0fa067a47c7f        ceosimage:4.23.2F                                     "/sbin/init systemd.…"   About a minute ago   Up About a minute                       ceos_vms6-1_VM0101
47066451fa4c        debian:jessie                                         "bash"                   About a minute ago   Up About a minute                       net_vms6-1_VM0101
e07bd0245bd9        ceosimage:4.23.2F                                     "/sbin/init systemd.…"   About a minute ago   Up About a minute                       ceos_vms6-1_VM0100
4584820bf368        debian:jessie                                         "bash"                   7 minutes ago        Up 7 minutes                            net_vms6-1_VM0100
c929c622232a        sonicdev-microsoft.azurecr.io:443/docker-ptf:latest   "/usr/local/bin/supe…"   7 minutes ago        Up 7 minutes                            ptf_vms6-1

Cisco

Now we need to spin up some VMs on the host to act as neighboring devices to our virtual SONiC switch.

Start the VMs:
```
./testbed-cli.sh -m veos_vtb -k vcisco -t vtestbed.yaml start-topo-vms vms-kvm-wan-pub-cisco password.txt
```
Verify that the vcisco neighbors were created properly: Because cisco devices can't run ansible module smoothly, we can manually ssh to these VMs to verify whether devices startup normally.

Deploy topology

cd /data/sonic-mgmt/ansible
./testbed-cli.sh -t vtestbed.yaml -m veos_vtb -k vcisco add-topo vms-kvm-wan-pub-cisco password.txt

Deploy configuration on the devices

Once the topology has been created, we need to give the devices an initial configuration.

cEOS:

./testbed-cli.sh -t vtestbed.yaml -m veos_vtb deploy-mg vms-kvm-wan-pub veos_vtb password.txt

cisco:

./testbed-cli.sh -t vtestbed.yaml -m veos_vtb deploy-mg vms-kvm-wan-pub-cisco veos_vtb password.txt

Verify the DUT is created successfully. In your host run

~$ virsh list
 Id   Name      State
-------------------------
 3    vlab-01   running

Then you can try to login to your dut through the command and get logged in as shown below. For more information about how to get the DUT IP address, please refer to doc testbed.Example#access-the-dut

~$ ssh admin@10.250.0.101
admin@10.250.0.101's password:
Linux vlab-01 4.19.0-12-2-amd64 #1 SMP Debian 4.19.152-1 (2020-10-18) x86_64
You are on
 ____   ___  _   _ _  ____
/ ___| / _ \| \ | (_)/ ___|
\___ \| | | |  \| | | |
 ___) | |_| | |\  | | |___
|____/ \___/|_| \_|_|\____|

-- Software for Open Networking in the Cloud --

Unauthorized access and/or use are prohibited.
All access and/or use are subject to monitoring.

Help:    http://azure.github.io/SONiC/

Last login: Thu Jul 29 03:55:53 2021 from 10.250.0.1
admin@vlab-01:~$ exit

Verify that you can login to the SONiC KVM using Mgmt IP = 10.250.0.101 and admin:password.
```
ssh admin@10.250.0.101
admin@10.250.0.101's password: password
```

After logged in to the SONiC KVM, you should be able to see IP interfaces with:

show ip int

admin@vlab-01:~$ show ip int
Interface       Master    IPv4 address/mask    Admin/Oper    BGP Neighbor    Neighbor IP
--------------  --------  -------------------  ------------  --------------  -------------
Loopback0                 10.1.0.32/32         up/up         N/A             N/A
PortChannel101            10.0.0.56/31         up/up         N/A             N/A
PortChannel102            10.0.0.58/31         up/up         N/A             N/A
docker0                   240.127.1.1/24       up/down       N/A             N/A
eth0                      10.250.0.101/24      up/up         N/A             N/A
lo                        127.0.0.1/16         up/up         N/A             N/A
admin@vlab-01:~$

Run a Pytest

Now that the testbed has been fully setup and configured, let's run a simple test to make sure everything is functioning as expected.

Switch over to the tests directory:
```
cd sonic-mgmt/tests
```
Run the following command to execute the lldp test (including the pre/post setup steps):

If neighbor devices are EOS

./run_tests.sh -m group -a False -n vms-kvm-wan-pub -u -d vlab-01 -c wan/lldp/ -f vtestbed.yaml -i veos_vtb -e "--neighbor_type=eos --disable_loganalyzer --skip_sanity"

If neighbor devices are Cisco

./run_tests.sh -m group -a False -n vms-kvm-wan-pub-cisco -u -d vlab-01 -c wan/lldp/ -f vtestbed.yaml -i veos_vtb -e "--neighbor_type=cisco --disable_loganalyzer --skip_sanity"

You should see tests run and pass. You're now set up and ready to use the KVM testbed!

Restore/Remove the testing environment

If you want to clear your testing environment, you can log into your mgmt docker that you created at step three in section Prepare testbed host.

Then run command: For cEOS neighbor:

./testbed-cli.sh -t vtestbed.yaml -m veos_vtb -k ceos remove-topo vms-kvm-wan-pub password.txt

For cisco neighbor:

./testbed-cli.sh -t vtestbed.yaml -m veos_vtb -k vcisco remove-topo vms-kvm-wan-pub-cisco password.txt