By: George Djaboury, Senior Network Engineer, SMS
The purpose of this post is to perform a basic setup of Ansible on Eve-NG. If you are a network engineer who has never been exposed to Ansible before, then this is perfect for you. By the end of this tutorial, you will be able to successfully push configurations to network devices via Ansible, and you’ll have the building blocks to begin constructing your own playbooks. Let’s get started!
– Eve-NG installed
– Ubuntu Server VM installed and has IP connectivity to the internet and routers in the lab environment.
– Router images must support SSH – Cisco images must have “k9” on the OS name
– “Linux-ubuntu-18.04-server” – downloaded from the Eve-NG website. They have several Linux images (mostly out of date). Updating images after installation is always recommended. I updated the image to the latest version – Ubuntu Server 22.04 LTS. Eve-NG also supports custom images.
– Routers1 and 2 (CSRv): csr1000vng-universalk9.16.03
– Router3: c7200-adventerprisek9-mz.152-4.M7.bin
– Switch: i86bi-linux-l2-adventerprise-15.1b.bin – any layer 2 image will be sufficient
The Eve-NG topology is simple, but you don’t need much get started pushing configurations with Ansible.
Inserting a “Network” type object is required for internet access. The Linux server just needs to be able to pull updates and download Ansible. I used the “Management(Cloud0)” type in this lab.
Add an object -> Network
Ensure the Linux server can ping all Routers before proceeding
Enable SSH on Routers
A basic configuration is needed to enable SSH. Ansible utilizes SSH by default to connect to all hosts.
Verify crypto keys are generated:
Verify SSH from Ubuntu Server to Routers
Ansible requires the crypto keys of the remote devices before it can connect via SSH. Let’s see if we can SSH.
Looks like SSH failed since the images in my lab use older algorithms that is not compatible with Ubuntu Server 22.04 LTS. To get around this, we have to create the user SSH configuration file and insert compatible ciphers/algorithms.
Restart SSH and try again.
SSH still failed. I’ll need to add the ssh-rsa key type in the config file based on what the router is offering
Save the file, restart SSH, and give it another try.
It worked! Now SSH to your remaining Routers.
If you need to remove a learned key in Ubuntu for some reason (e.g. SSH key changed), then type:
We are now ready to setup the server with Ansible!
Installation and Setup of Ansible on Ubuntu
The first step is to update the server to the latest version.
To install Ansible, it’s best to follow instructions on Ansible Documentation website.
Verify Ansible installation by checking the version:
Additionally, we need to install LibSSH, needed to connect to network devices, and is replacing paramiko.
Creating the inventory file
The /etc/ansible file directory should have been created; if not, create it. Navigate to the ansible directory and view its contents. The ‘hosts’ file is the default Ansible inventory file.
Now let’s add our routers in the hosts file:
It’s a good idea to use groups by enclosing the group name in brackets. The first group comprises of all our lab IOS routers. The second group defines the variables for the iosrouters group. For a lab environment, it’s ok to insert plain-text creds in here.
After saving the inventory file, you can verify variables have applied to each host:
Creating a Playbook
All playboooks must be written in YAML format with .yml or .yaml file extension.
Create a “playbooks” folder and a new playbook file. This playbook is using the “ios_config,” “ios_static_route,” and “ios_banner” modules. This playbook defines 4 different tasks.
Run Ansible playbook
For each task, it displays the status of the task for each device; the state of the task displays “changed.”
Now run the same playbook, but with the –check option. This option simulates what would happen if the playbook was actually pushed, but without making changes.
Notice the states of the tasks in the left column, which declares “ok” instead of “changed.” Ansible will not execute a task if the desired state is already achieved.
Setup is now complete! While that completes this initial task, I encourage you to keep learning; search for different Ansible modules and use them in different playbooks. Ansible can be a powerful tool in your automation toolbox!
For network engineers just getting started with Ansible, I highly recommend going through the Network Automation resource on the Ansible website.