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Cisco NX-OS Network Automation using Python
Network Automation
- Process of using software to automate network provisioning, testing, deployment and network management
- To help maximize network efficiency and functionality
- Networks are complex and bulky in nature
- Manual operations – more delays
- Automation makes the networks more agile and responsive to changes
- Benefits:
- Improved operational efficiency
- Reduced errors
Network Automation Architecture
Network Programmability
- It’s a set of tools to deploy, manage and troubleshoot a network device
- Network engineer perspective – interacting with a device or group of devices
- Software developer perspective – abstracting the network. Seeing the whole network as a single device and manipulating it with software
Benefits of Network Programmability
- Reduced OPEX
- Customization
- Reduced human error
- Operational flexibility
- Increased opportunity for innovation
Application Programming Interface (API)
- APIs are mechanisms used to communicate with applications and other software.
- An API may perform different functions based on where they are located in the flow
- Used to communicate with various components of the network through software
- APIs are usually RESTful APIs
Representational State Transfer (REST) APIs
- An API that uses REST is often referred to a RESTful API
- RESTful APIs use Hypertext Transfer Protocol (HTTP) methods to gather and manipulate data.
| HTTP Function | Action |
| GET | Read |
| POST | Create |
| PATCH | Update / Modify |
| PUT | Update / Replace |
| DELETE | Delete |
HTTP Status Codes
| HTTP STATUS
CODE |
RESULT | COMMON REASON |
| 200 | Ok | Using GET or POST to exchange data with
an API |
| 201 | Created | Creating resources by using a REST API call |
| 400 | Bad Request | Request failed due to client-side issue |
| 401 | Unauthorized | Client not authenticated to access site or
API call |
| 403 | Forbidden | Access not granted based on supplied
credentials |
| 404 | Not Found | Page at HTTP URL location does not exist
or is hidden |
Netmiko Overview
- Netmiko – Python library used extensively to interact with network devices
- Multi-vendor library
- Cisco IOS/IOS-XE, NX-OS, firewalls, etc.
- Extended support of Paramiko library’s SSH functionality
- Going into configuration modes
- Sending commands
- Retrieving outputs
- Taking care of yes/no prompts
NAPALM Overview
- NAPALM – Network automation and programmability abstraction layer with multi-vendor support
- Provides functions that allows:
- Configuration operations (commit or rollback)
- Retrieve state data from network devices
- Contains methods to establish connection to network devices
- Can work in conjunction with automation tools – Ansible
- Has support for various network OS:
- IOS, IOS-XR, NX-OS, JunOS, EOS, etc.
NAPALM Operations
- Replace – Allows users to replace the existing running configuration with an entirely new configuration.
- Merge – Allows users to merge configuration changes from a file to the running configuration on the device.
- Compare – Compare the newly proposed configuration with the existing one. Only applies to replace operation and not for merge operation.
- Discard – Resets the merge configuration file to an empty file. Thus, not allowing the new configuration to be applied on the device.
- Commit – Commits the proposed configuration to the network device. In other words, used to deploy a staged configuration.
- Rollback – Rollback (revert back) the running configuration to the saved configured prior to the last commit.
Templating with Jinja2
- Jinja is a modern templating language for Python – Modelled after Django templates
- Allows user to easily interact with Python program
- Use data to quickly generate dynamic content
- Benefits:
- Template inheritance
- Optimal just-in-time compilation
- Easy debuggability
- Configurable syntax
- Commonly used with web frameworks such as Flask
- Configuration management tools – Ansible, Nornir, etc.
Delimiters
Nornir Overview
- Python based automation framework
- Manage network and host inventory and provide common framework to write plugins for the network devices and hosts
- Requires minimum Python version 3.6.2
- Multi-threaded – Defaults to 20 worker threads
- Initialized using config file – references couple other files
- Host inventory file
- Group file
- All these files are written in YAML format
Nornir Advantages
- Python or Golang (Gornir)
- Reuse existing libraries – napalm, netmiko
- Quick host filtering based on any attribute or combination of attributes
- Very fast due to use of threads
- Can be used to build highly flexible and extensible automation tools using Flask, Django, etc.
- Automatically performs caching and closes open connections
Extra Resources and References
Cisco Press News
Network Programmability and Automation Fundamentals [Learn more] CCNP and CCIE Security Core SCOR 350-701 Official Cert Guide
https://www.ciscopress.com/store/ccnp-and-ccie-security-core-scor-350-701-official-cert-9780135971970
Cisco DevNet Professional DEVCOR 350-901 Study Guide
https://www.ciscopress.com/store/cisco-devnet-professional-devcor-350-901-study-guide-9780137500048
Other useful resources:
Interview with Vinit Jain, Cisco’s Top Events Contributor
https://community.cisco.com/t5/networking-documents/interview-with-vinit-jain-cisco-s-top-events-contributor/ta-p/3156059
Vinit’s publications
http://www.ciscopress.com/authors/bio/255ee209-1418-4938-9a42-d3bece2b46c6
Documents / Resources
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Cisco NX-OS Network Automation using Python [pdf] User Manual NX-OS Network Automation using Python, Network Automation using Python, using Python |
