Network Automation using Ansible for Cisco Routers Basic Configuration

Network Automation using Ansible for Cisco
Routers Basic Configuration
Jonathan Wijaya
Telematics Laboratory, School of Electrical Engineering and Informatics,
Bandung Institute of Technology, e-mail: [email protected]
Abstract: Network programmability is a trend,
protocols, like OpenFlow. However, the
enhanced and inspired by Software Defined
“traditional” non-SDN legacy networks need to
Networks, that are based on scripting methods
keep the pace and respond to dynamic network
and standard programming languages used for
changes. Network automation is a solution for
controlling
network
operational expenses saving, improving not
elements. This paper is illustrating a method in
only the time spent for configuring the network
configuring
using
devices, but also the efficiency of network
automation, reducing time for equipment
maintenance through procedures that are easier
configuration and easier maintenance. It uses
to follow and implement at large scale.
and
monitoring
network
devices
of
by
Ansible in Ubuntu environment as the
controller, and Cisco routers as the managed
All major vendors, including Cisco, started
nodes. These methods represent the future of
promoting the software configurability of
networks, allowing the management of an
networks (e.g. Cisco DevNet concept that
increased number of devices in a unitary way.
promotes the creation of an open source
community for network programmability [5]).
Keywords: Network, Automation, Ansible.
All new automation implementations are based
on generic programing methods (python, java)
1. Introduction
and standard interfaces (Secure Shell SSH or
even RESTful webservices).
The number of devices in a network and their
heterogeneous nature is steadily increasing.
However, only the newer devices have support
The traditional methods used for network
for the new programmatic methods, and this
equipment configuration are time consuming,
paper addresses methods to automate legacy
taking into consideration also the vendor
network elements.
specific know-how needed. The Software
Defined Networks (SDN) concept tries to
The main objective of this paper is to
eliminate the vendor dependency via standard
demonstrate the efficiency of the scripting in
configuring network devices. For that we have
parts, usage of OpenSSH for transport (with
created an emulated network topology in Eve-
other transports and pull modes as alternatives),
ng, having as main element an Ubuntu Desktop,
and a language that is designed around
with the role of a network controlling element.
auditability by humans–even those not familiar
We have controlled the network devices in a
with the program.
programmatic way using Ansible, based on
Python.
Ansible is appropriate for managing all
environments, from small setups with a handful
2. Network Automation using Ansible
of instances to enterprise environments with
many thousands of instances.
At its core, network automation has the main
goal of simplifying the tasks involved in
Ansible manages machines in an agent-less
configuring, managing and operating network
manner. There is never a question of how to
equipment,
network
upgrade remote daemons or the problem of not
services and network connectivity. In my
being able to manage systems because daemons
experimental setup I have used the Eve-ng
are uninstalled. Because OpenSSH is one of the
emulator which is a tool for building, designing
most peer-reviewed open source components,
and testing networks, capable now also to
security exposure is greatly reduced. Ansible is
connect to external networks and allowing
decentralized–it relies on your existing OS
integration with virtual images.
credentials to control access to remote
network
topologies,
machines. If needed, Ansible can easily connect
A. Network Setup
with Kerberos, LDAP, and other centralized
authentication management systems.
For the specific implementation, I have used an
Ubuntu Desktop which is running Ansible,
The scripts incorporate some functionalities
allowing to connect to devices and automate
like
their configuration via ssh connections.
configuration, and routing protocols. The
hostname
changing,
IP
address
scripts can be used for almost all network
Ansible is an IT automation tool. It can
devices regardless of the vendor that produces
configure systems, deploy software, and
them.
orchestrate more advanced IT tasks such as
continuous deployments or zero downtime
The topology contains a cloud (Net) which is
rolling updates.
used to connect the Ubuntu Desktop device
which will run the Ansible and its automated
Ansible’s main goals are simplicity and ease-
scripts for configuring network devices, a
of-use. It also has a strong focus on security and
Switch (using Cisco vIOS) that is making the
reliability, featuring a minimum of moving
connection
to
2
Routers
that
will
be
automatically configured (Figure 2.1).
Packaging Tool (APT) in Ubuntu. The
following commands
will
configure
the
Personal Package Archives (PPA), install
Ansible, and install the newest python version.
$ sudo apt update
$ sudo apt install softwareproperties-common
$ sudo apt-add-repository
ppa:ansible/ansible
$ sudo apt update
$ sudo apt install ansible
$ sudo apt install python
Figure 2.1 Topology
B. Ansible Automation Methods
The Ubuntu Desktop needs to be in the same
There are 3 main file in the Ansible directory,
network as the devices that we want to
hosts, ansible.cfg, and Ansible Playbook file.
automatically configure so it can obtain an IP
The hosts file is the inventory file where we add
via a common DHCP or we can configure a
our managed nodes to be controlled by Ansible.
static IP address. It also must be connected to
Ansible.cfg is the actual configuration file used
Internet for downloading the necessary tools.
to tweak Ansible parameters. Once the
installation is done, we need to add some nodes
The routers need to be configured first. What
in the hosts file. In my case I add 2 IP addresses
needs to be configured are IP address of the
which belong to interface fa0/0 of my 2 routers.
connected interface and SSH, so that the
Here is the content of my hosts file:
controller (Ubuntu Desktop) can access the
//hosts
[iosxr]
10.10.1.99
10.10.1.199
routers.
An Ansible controller (the main component that
manages the nodes), is supported on multiple
flavors of Linux, but it cannot be installed on
Windows. For managed nodes, since Ansible
uses SSH to communicate with managed nodes,
the node must be able to be accessed from SSH.
Going back to controller machine installation,
Python 2 (2.6 or above) needs to be installed. In
my case, I am using Ubuntu as my OS, hence
my focus would be on working with Ansible
using Ubuntu as the underlying OS. A way of
installing Ansible is to use the Advanced
I grouped the 2 hosts with a group name ‘iosxr’
because they are Cisco routers using iosxr
operating system. Then after the hosts file, the
other file is the Ansible Playbook. Ansible
playbook contains the configuration we want to
push to the devices. The playbook file has ‘.yml’
file extension. In my case, the contents of my
playbook file are the routers’ username and
password, hostname configuration, IP address
configurations, and OSPF configuration. Here
is the content of my playbook file:
//ansible-playbook
--- name: config
hosts: all
connection: local
gather_facts: no
tasks:
- name: configure provider
set_fact:
provider:
username: cisco
password: cisco
- name: set hostname
ios_config:
provider: "{{provider}}"
lines: hostname
{{ inventory_hostname }}
- name: interface IP address
ios_config:
provider: "{{provider}}"
lines:
- ip address 192.168.1.10
255.255.255.0
- no shutdown
- full-duplex
parents: interface
FastEthernet 1/0
- name: loopback interface
ios_config:
provider: "{{provider}}"
lines:
- ip address 1.1.1.1
255.255.255.255
- no shutdown
parents: interface
Loopback0
- name: configure ospf network
ios_config:
provider: "{{provider}}"
lines:
- router-id 1.1.1.1
- network 192.168.1.10
0.0.0.255 area 0
parents: router ospf 1
Figure 2.2 Ansible Playbook Result
Figure 2.2 above shows the result after I run the
playbook file. The result shows that I
successfully changed 4 configurations in the
target routers. Those 4 configurations are
hostname, interface IP address, loopback IP
address, and OSPF.
For my future work I plan to automate network
devices using Ansible alongside NAPALM.
Network Automation and Programmability
Abstraction Layer with Multivendor support
[9] is a Python library that implements a set of
functions to interact with different router
vendor devices using a unified API. The
heterogeneous vendors are integrated via
drivers, and NAPALM offers support for most
of the important vendors.
After making sure the files’ contents are correct,
what we need to do is just run the playbook file.
3. Conclusions
In my case, my playbook file’s name is
‘test.yml’, so what I need to type is:
ansible-playbook test.yml
Configuring and monitoring any device via
automation, independent of vendors is a goal
implementable not only on SDN devices, but
also on other networking solutions. In this
paper, I have demonstrated the importance of
automation in a network that are not aware of
OpenFlow SDN protocol.
I have demonstrated that using Ansible,
network engineers do not need to configure by
themselves each individual device, they just
need to create the proper infrastructure and by
implementing
automation
scripting.
The
network controllability becomes easier and
changes can be faster deployed, maybe even
automatically, as response to events that take
place in the network. So the legacy network
elements becoming similar with SDNs.
Reference
1. Ansible for Network Automation, https://docs.
ansible.com/ansible/latest/network/index.html
2. Tischer R., Gooley J. 2016. Programming and
Automating Cisco Networks. Cisco Press.
3. Cisco ”DevNet” Open Source Dev Center https://developer.cisco.com/site/opensource/
4. NAPALM (Network Automation and Programmability Abstraction Layer with Multivendor support) https://napalm.readthedocs.io/
en/latest/
5. Ansible for Network Automation Tutorial,
https://www.networkcomputing.com/networkin
g/