Ansible + Arista Quick Start

A simple Ansible setup to get you up and running faster!

Intro

This repo includes automated playbooks that will help you run some basic playbooks against your Arista EOS switch. This setup is not meant to be a boilerplate for production, rather, a quick and easy way to learn the basics. Instead of dealing with system-specific install issues with Ansible, this quickstart has you run Ansible from Docker.

Prereqs

• Docker
• A CLI user created on your switch
• An Arista EOS switch with eAPI enabled or SSH access

Getting Started

First clone this repo

git clone https://github.com/arista-eosplus/eos-ansible-quick-start.git
cd eos-ansible-quick-start

Create the Docker Image

docker build -t ansible .

Note: If you want to run Ansible from Source, run:

docker build -t ansible-dev -f ./Dockerfile-dev .

Run the Container

docker run -i -t -v $(pwd):/ansible-sample ansible

Note: The -v will mount the files in this quickstart repo into the root of the docker container. You will find this in /ansible-sample. If you created the development version, substitute ansible with ansible-dev

Run the Setup Playbook

cd /ansible-sample
ansible-playbook setup_env.yaml

You'll answer a few basic questions to help get your files setup.

What is the IP or FQDN of your EOS device?: 172.16.130.201
How would you like to connect to the switch? [ssh|http|https]: http
EOS Username?: admin
EOS password?:
Do we need to run 'enable' upon login? [yes|no]: no

Then some tasks will run to:

• Create a group_vars/all file. Notice there's a provider dict with values you entered in the prompt.
• Create a hosts file containing the host
• A host_vars/<host> with some basic vars to get you up and running.

Run your first EOS playbook

ansible-playbook -i hosts base_configuration.yaml -v

You should get something like:

PLAY [all] *********************************************************************

TASK [Arista EOS Base Configuration] *******************************************
changed: [172.16.130.201] => {"changed": true, "responses": [{}, {}, {}, {}], "updates": ["ip name-server vrf default 8.8.8.8", "ip name-server vrf default 2.2.2.2", "hostname arista.makes.the.best.switches", "ip name-server vrf default 1.1.1.1"]}

PLAY RECAP *********************************************************************
172.16.130.201             : ok=1    changed=1    unreachable=0    failed=0

Cool! So by looking at the updates field we see that we configured some DNS servers and the hostname! Easy peasy!

Run it again to see idempotency in action. That's to say, if Ansible sees that all of the config on the switch is in the state we define in our playbook don't make any changes!

PLAY [all] *********************************************************************

TASK [Arista EOS Base Configuration] *******************************************
ok: [172.16.130.201] => {"changed": false, "updates": []}

PLAY RECAP *********************************************************************
172.16.130.201             : ok=1    changed=0    unreachable=0    failed=0   

Notice now that the task comes back 'ok' and there are no changed items.

How it works

Let's break down the playbook command:

ansible-playbook -i hosts base_configuration.yaml -v

This says:

• Use the ansible-playbook command to run a playbook
• We use the -i hosts to specify our local hosts file instead of the default one in /etc/ansible/hosts
• We want to run the base_configuration.yaml playbook
• We want to see some extra logging with -v verbosity

Let's take a look inside this playbook:

---
- hosts: eos_demo_group
  gather_facts: no
  connection: local

  tasks:
    - name: Arista EOS Base Configuration
      eos_template:
        src=baseconfig.j2
        provider={{ provider|default(omit) }}

First we specify the group of hosts that we want to run this playbook against. In this case, it will look in the hosts file for the eos_demo_group group and run the playbook against all the hosts inside.

Then we skip generic fact gathering with gather_facts: no

Importantly, we use connection: local. This tells Ansible to run the modules locally. If we didn't use this, Ansible would try and SSH into our host and look for a bash shell. This isn't the same type of SSH connection that we use to access the CLI.

Then we move on to tasks. In this case we simply run one task to setup some basic config. This task uses the eos_template module to execute a Jinja template, then compare the generated config against the EOS running-config. If it determines there are incongruities, it will issue the needed commands to get the switch config into the correct state.

Let's take a look at this Jinja template, baseconfig.j2:

hostname {{ hostname }}

{% for dns_ip in dns_servers %}
ip name-server vrf default {{ dns_ip }}
{% endfor %}

Jinja is pretty easy to read. The {{ denote a variable to be substituted. Ansible will look for a variable called hostname and put it in there. In this setup, it finds it in the host_vars/<host> file. Try changing the hostname variable in host_vars/<host> and re-run your playbook to see the hostname change (where is the host FQDN/IP you provided earlier).

Then we get to some cool Jinja control logic. If you've worked with Python, the loop we have here should look very familiar. Ansible automatically takes the dns_servers list from group_var/all.yaml and creates a config line for each entry. What do you think would happen if you created a dns_servers list in your host_vars/<host> file? Give it a try and re-run the playbook!