Python for the Network Nerd

Python
For the Network Nerd
By Matt Bynum, A Network Nerd

About Me
● In IT for a total of 14 years
● Doing Networking and VoIP for 13 of those
● Consulting for 8 years
● Leading a consulting practice for 2 years
● Programming in Python for 3 Months
Disclaimer: I am not a Python expert.

APIs
SDN
Automation
Open Source

Python Basics
Working through SSH
Importing Devices from CSV
Building Config Templates
What to do Next

● Variables are references to objects.
● Objects can be built-in like strings, or “things” that can
be manipulated or passed around.
● Lists contain objects.
● Dictionaries are containers that use key:value pairing to
store objects, and coincidentally, are also objects
themselves.
● Libraries are Python packages that can be used over
and over
Python Fundies

● myVar = “this is a string”
● WAN01 = Router()
● [WAN01, WAN02, CORE01, CORE02]
● {‘ip’: ‘10.0.0.1’, ‘username’: ‘cisco’, ‘password’: ‘cisco’}
● import csv
Python Fundies (cont.)

What version of Python?
Stick with Python 2 for now.

Recommended Python Tutorials
Codecademy.com
Udacity.com
LearnPythonTheHardWay.org
edX.org Intro to CompSci

“But why not Telnet, Mr. Presenter?”

Netmiko
● Based on Paramiko
● Created by Kirk Byers, a CCIE R/S Emeritus
● Found on GitHub: https://github.
com/ktbyers/netmiko
● Designed for Network Devices

Netmiko - Setup
import netmiko
device = {'ip': '192.168.0.1', 'username': 'admin', 'password': 'password123', 'secret':
'secret123', 'verbose': False}
SSHClass = netmiko.ssh_dispatcher(device_type="cisco_ios")
net_connect = SSHClass(**device)

Netmiko - Commands
# Single Command
output = net_connect.send_command(“show run | i snmp”)
print output
# Multiple Commands
commands = [“show ip int brief | e unass”, “show ip route”, “show cdp neighbors”]
for command in commands:
output += net_connect.send_command(command)
print output

Netmiko - Configs
config = [“interface gig 0/0/1”, “description Uplink to Core”, “switchport mode trunk”]
net_connect.send_config_set(config)

Netmiko - Multi-device
yourDevices = [{'ip': '192.168.0.1', 'username': 'admin', 'password': 'password123',
'secret': 'secret123', 'verbose': False},{'ip': '192.168.0.2', 'username': 'admin',
'password': 'password123', 'secret': 'secret123', 'verbose': False}]
SSHClass = netmiko.ssh_dispatcher(device_type="cisco_ios")
net_connect = SSHClass(**yourDevice)

Netmiko - Multi-device cont.
commands = [“show ip int brief | e unass”, “show ip route”, “show cdp neighbors”]
for each in yourDevices:
net_connect = SSHClass(**each)
output = ''
for command in commands:
output += net_connect.send_command(command)
print output

Comma Separated Values
import csv
devices = []
devicesDict = {}
with open(“c:routers.csv”) as devicesFile:
devicesDict = csv.DictReader(devicesFile, dialect='excel')
for row in devicesDict:
devices.append(row)

CSV Output
[{'username': 'mbyn', 'verbose': 'True', 'ip': '172.20.5.14', 'hostname':
'TEST_DEVICE_1', 'secret': '', 'password': 'fakepw'},
{'username': 'mbyn', 'verbose': 'True', 'ip': '172.20.5.15', 'hostname':
'TEST_DEVICE_2', 'secret': '', 'password': 'fakepw'},
...]

Jinja2 Templates
{% if interface %}
int {{ interface }}
{% endif %}
{% if description %}
description Uplink from {{ hostname }} to {{ description }}
{% endif %}

Python Jinja2
import jinja2
device = {'hostname': 'DIST01', 'ip': '192.168.0.2', 'username': 'admin', 'password':
'password123', 'secret': 'secret123', 'verbose': False, 'interface': 'gig 0/0/1',
'description': 'CORE SWITCH 1'}
env = jinja2.Environment(loader=jinja2.FileSystemLoader('templates'),trim_blocks=True)
commands = env.get_template(“template.cfg”).render(device)

Rendered Configuration
int gig 0/0/1
description Uplink from DIST01 to CORE SWITCH 1

What to do Next
“The future belongs to those who see possibilities before they become obvious.”
- John Sculley

Things to work on
● Scripting VLAN Moves/Adds/Changes, QoS
deployments, any other bulk changes
● Configuration Auditing
● APIs
● SNMP collection and graphing
● Using YAML and JSON for templating config
elements

Where your job is heading
DevOps
SDN
Automation and Orchestration

Python for the Network Nerd

More Related Content

What's hot

Viewers also liked

Similar to Python for the Network Nerd

More from Matt Bynum

Recently uploaded

Python for the Network Nerd