The document discusses using Ansible and NX-API to automate Cisco Nexus switches. It demonstrates generating configuration templates from Ansible roles and templates. A Python module is used to apply the configurations to Nexus switches via NX-API REST API. The process flow shows Ansible modules generating configuration files which are then installed on Nexus switches via the NX-API REST interface.

1. Copyright © 2015 World Wide Technology, Inc. All rights reserved.
Software-Defined Networking
Network Automation with Ansible and NX-API
Joel W. King
Technical Solutions Architect
Enterprise Networking Solutions
Engineering and Innovations

2. Goals
• Demonstrate NX-API
• NX-API is an enhancement to the Cisco Nexus 9000 Series (CLIs) system.
• NX-API uses HTTP/HTTPS to make CLI commands available to the network programmer
outside of the switch.

3. Nexus Programmability
Power
On
Auto
Provisio
ning
(POAP)
Nexus Programmability
onePK
API
Nexus 9K
NX-API
RPC / REST API
Python
Interpreter
Super
commands
-
Software-
Defined
Network
Programming
Class
OpenFlow | XNC
XNC Monitor
Manager Demo
w/ Python REST
API
NXOS ACI
Orchestration
APIC
REST API
Matrix Switch
QualiSystems
XNC
Security-Defined
Routing

4. Goals
• Demonstrate NX-API
• NX-API is an enhancement to the Cisco Nexus 9000 Series (CLIs) system.
• NX-API uses HTTP/HTTPS to make CLI commands available to the network programmer
outside of the switch.
• Demonstrate orchestration of enhanced NX-OS
• Ansible proved interesting because:
• Agentless
• uses Open SSH for transport
• Written in Python
• Improve your value as a network engineer

5. What do Network Engineers Need?
• A toolset which doesn’t require programming skill to be usable, but allows user written
modules if required.
• While existing tools are end node (server) oriented, NetOps need tools which can be used in
the hierarchical nature of networks.
• Resources to test automation tools, e.g. virtual routers
• Agents or Agentless?
• Automation tools which don’t require agents running on the end nodes (routers / switches)
• Network Configuration Protocol (NETCONF) defines an XML-based interface between a network
device and a network management system to provide a mechanism to manage, configure, and
monitor a network device.
• Drawback for IT tools like Puppet and Chef, is they require agents.
• Ansible is great for VARs to upgrade and install equipment for their customers.

6. NX-API
• What is NX-API?
• Enhancement to the Cisco Nexus 9000 Series command-line interfaces (CLIs) system.
• NX-API support on Nexus 3000 series starting with NX-OS 6.0(2)U4(1).
• Uses HTTP/HTTPS to make CLI commands available to the network programmer outside
of the switch.
• Supports show commands,
configurations, and Linux Bash.
• Nexus 9Ks in Non-ACI mode
• feature nxapi
HTTP/HTTPS

7. Ansible
• Ansible began as a project about February of 2012, out of a need for a simpler automation
tool than existed in Puppet and Cobbler.
• Does not require custom scripting or code.
• Designed to be easy for anyone to understand and learn.
• Ansible Design Principles:
• Simply Clear no gnarly scripts or custom code
• Simply Fast minimal learning curve
• Simply Powerful toolbox for automation
• Simply Efficient agentless - lightweight and unobtrusive
• Simply Secure no agent on managed hosts – uses OpenSSH
• ANSIBLE HQ in Durham NC
• Ansible Tower adding over two customers a day

8. Agentless
Efficient Architecture
• Open source system automation tool
• Connects to systems and pushes out Python programs - “Ansible Modules”
• Executes modules via SSH and removes the module when finished.
• Modules reside on any machine, no server, databases required.
• Playbooks, written in YAML, configuration, deployment, orchestration language
• Ansible ships with a module library
• Ansible is primarily used for working with server operating systems,
• Majority of the modules are focused on server administration.
• Modules can be locally written and added to the library, e.g. https://github.com/joelwking

9. Ansible Tower: Commercial GUI for Ansible

10. Lexicon
• Inventory
• Playbooks
• YAML a data serialization
format
• Facts
• Variables
• Modules
• Roles
• Idempotent(*)
• Agentless
• Jinja2
(*) http://en.wikipedia.org/wiki/Idempotence

11. Playbooks
• Playbooks are Ansible’s configuration,
deployment, and orchestration
language.
• Ansible modules are the tools in
your workshop,
• Playbooks are your design plans.

12. Inventory
Host Inventory is maintained in text files
• INI files are used to define managed hosts
• INI format is human-readable and simple to parse programmatically
• Hosts can be assigned to groups
[sample]
localhost ansible_connection=local ansible_ssh_user=administrator
[nexus9k]
raleigh
cary
durham

13. Variables
Variables can be associated with hosts or groups
~/ansible/
~/ansible/host_vars ~/ansible/group_vars
cat ~/ansible/host_vars/cary
host : 10.255.139.185
int_ip : 192.0.2.1
cat ~/ansible/host_vars/raleigh
host : 10.255.44.44
int_ip : 192.0.2.3
cat ~/ansible/group_vars/nexus9k
#
int_mask: 255.255.255.255
Variables can also be specified in the playbook.

14. Modules
• Modules typically are executed through Playbooks
• Playbooks are likely to be managed with a source control / versioning system
• Arguments are specified in the playbook, host_vars, group_vars or host files
• ~/ansible/bin/ansible-playbook -i ansible_hosts/ansible_hosts ./SAMPLE_FILE_XFER.yml
• For ad-hoc tasks, your can run the main Ansible program
• Arguments to the module specified on the command line
• ~/ansible/bin/ansible nexus9k -m nxapi-module.py -a "show=version" -i ./ansible_hosts
• For module development, use the test module
• ~ansible/hacking/test-module -m /tmp/nxapi-module.py -a "show='banner motd'
host=10.255.139.185"

15. Copyright © 2015 World Wide Technology, Inc. All rights reserved.
Software-Defined Networking
Ansible Nexus 3000 Series Lab
Joel W. King
Technical Solutions Architect
Enterprise Networking Solutions
Engineering and Innovations

16. Demonstrations
• Uses Ansible roles organizational feature for templates, tasks and variable files
• Creates router configuration files base on templates
• Invokes a Python module locally on the initiating host which reads the config files
• Uses nx-api (REST API) to apply the config to the Nexus 9K
Nexus 3000 Series
Top of Rack Switches
NEX-3048-Enex-3048-bNEX-3048-A
10.255.40.87 Interface mgmt010.255.138.6910.255.40.80

17. Process Flow
nxapi_install_config
nxapi_install_config
read configuration file
write log file
REST json-rpc
Nexus nx-api
9000 / 3000
Ansible module
or playbook
json
Arguments
hostname
host
userid pw
config_file
debug

18. Generate router configuration files from templates
administrator@api:~/ansible$ more nexus_cfg_builder.yml
---
- name: Generate nexus router config files
hosts: nexus9k
connection: local
gather_facts: no
roles:
- router
administrator@api:~/ansible$ ls ~/ansible/roles/router
tasks templates vars
---
- name: Generate Nexus configuration files
template: src=NEX-9396.j2 dest=/home/administrator/ansible/CFGS/{{hostname}}.txt
main.yml
#
no interface loopback{{loopback_number}}
interface loopback{{loopback_number}}
description {{hostname}}
ip address {{int_ip}}/{{int_mask}}
#
ntp server {{ntp_server}}
---
ntp_server : 10.255.139.129
NEX-9396.j2
main.yml
[nexus9k]
raleigh
cary
durham
ansible_hosts
host : 10.255.139.185
hostname : cary
int_ip : 192.0.2.1
host_vars/cary
group_vars/nexus9k
int_mask: 255.255.255.255
loopback_number : 99
./bin/ansible-playbook nexus_cfg_builder.yml

19. Execute the Playbook
• The playbook runs locally on the linux machine, creating the configuration templates

20. Resulting output files
$ cat NEX-3048-A.txt
#
# Nexus 3K template for Ansible Demo - joel.king@wwt.com - 18 Feb 2015
#
#
interface loopback99
description NEX-3048-A
ip address 203.0.113.1 255.255.255.255
#
no ntp server 10.255.139.129 use-vrf management
#
# if this statement exists you will get an error
#
ntp server 10.255.139.129 use-vrf management
#
logging timestamp milliseconds
#
logging level ftp 7
no logging console
#
copy run start
#

21. Ansible modules to automate Cisco NX-OS switches
https://github.com/datacenter/nxos-ansible
https://github.com/datacenter
https://github.com/joelwking