Locate IP devices on the wrong vlan

When replacing switches, sometimes a device like a Building Automation Control (BACnet) controllers or fire alarm quits working. This is usually because they got patched into the wrong port and now the IP address doesn’t work.

Since these devices normally have static IP addresses and seldom send a packet outbound, their MAC addresses don't register on the switch. This can lead to lost time and aggravation trying to get them back online, especially if they are in a remote cabinet or a switch that is physically hard to reach. This blog will show a process to reduce the time needed to locate the port the device is connected to, so that the problem can be resolved.

Here are the steps to take before the cutover

On the core switch

 

First, ping all host addresses for subnets of interest on the core switch. This will refresh the arp cache so that devices like BACnet controllers and alarms that have timed out will be in the cache. To do that:

• Execute show run | i ^_ip address - The i means include, the ^ means start at the first character, the _ means look for one space, and ip address is the string to look for. This regex returns just IP addresses from the SVIs, not every instance of the string ip address.
• Copy the output to a text file named vlans.txt
• Run the python3 script pinger.py - You can download the script and read its documentation here. This script converts the subnet address into hosts and pings each host.
• Execute show ip arp
• Copy the output to a text file named arp.txt
• Run the python3 script arp.py - You can download the script and read its documentation here. This script creates a json database of the MAC address/IP address mappings and is used with the next script.

On each edge switch

• Execute show mac add int g1/0/1 | i Gi for each edge port on the switch.
• Copy the output to a text file named mac-addr.txt. I created a spreadsheet with the necessary commands for several Cisco models and Rukus (Brocade) switches. You can download it here.
• Run the python3 script macaddr.py  - You can download the script and read its documentation here.

The last step creates a listing of switch ports with the IP address, MAC address, Port and MAC Manufacture: 

Device Name: Test.MDF
Vlan   IP Address       MAC Address       Type       Interface   Vendor
--------------------------------------------------------------------------------
  16   172.16.16.9        0020.4adb.3e21    DYNAMIC    Gi1/0/5     Pronet
--------------------------------------------------------------------------------
  26   172.16.26.94       54ee.7505.86b5    DYNAMIC    Gi1/0/14    WistronI
--------------------------------------------------------------------------------
  23   172.16.23.117      5442.49a1.06c6    DYNAMIC    Gi1/0/47    Sony
--------------------------------------------------------------------------------
  20   172.16.20.153      000c.820d.007e    DYNAMIC    Gi2/0/24    NetworkT
--------------------------------------------------------------------------------
  20   172.16.20.96       0040.9d97.a3aa    DYNAMIC    Gi2/0/26    Digiboar
--------------------------------------------------------------------------------
  20   172.16.21.96       cc72.0fff.f6a5    DYNAMIC    Gi2/0/27    Viscount
--------------------------------------------------------------------------------
  20   172.16.25.96       0024.7900.095b    DYNAMIC    Gi2/0/30    OptecDis
--------------------------------------------------------------------------------

For this example, I have trimmed the list so it only shows devices that I know are static IP devices like Pronet which is a serial to IP device server, Sony, which in this case is a Surveillance camera, Digiboard which is a serial to IP console server, etc.  These are all devices that are critical to the company's operation and I want to make sure they work after the cut over. 

The macaddr.py script also creates a section with just the IP address and MAC address. Here is a snippet of it:

Device Name: Test.MDF
PingInfo Data
172.16.16.9 0020.4adb.3e21
172.16.26.94 54ee.7505.86b5

I take that information and save it to a text file named PingInfo-xxx, where xxx is something meaningful for the site. I use the text file with a free program PingInfoView from www.nirsoft.net to create a dashboard of live ping results. Below is an example of a PingInfo dashboard. PingInfo is Windows only!

PingInfoView continuously pings the addresses and any address that stops responding turns red. Obviously, we want all addresses to be green after the cut over!

After the cut over

The PingInfo dashboard should be all green. But what do you do if one of the static ip devices isn't live in the dashboard? Since many of these devices are Operational Technology (OT) versus IT they seldom send any traffic onto the network so immediately after a cut over the port they are connected to won't have a MAC address. If it got connected to a port on the wrong vlan you won't be able to ping it to populate the MAC address table.

There is a Linux tool called arp-scan by Roy Hill that you can use to send arp requests to a device. It can also send arp requests with an 802.1q vlan tag. This is the key to finding the lost device.

How to use arp-scan

 

Here is the network diagram for our example:

In my lab, I used a Kali VM to simulate an OT device. At a real customer site, you obviously wouldn't know what port the device is connected to.

First, you will need to install arp-scan on the Ubuntu box:

sudo apt install arp-scan

You can use arp-scan --help to see all of the options for arp-scan. It has a lot of uses, if you Google arp-scan examples, you will find a lot of good ones. I wrote a pyhton script that uses arp-scan to find open IP addresses on a subnet. It's useful when you need to connect to a subnet that doesn't have DHCP but you don't want to cause an IP address conflict. You can download it here.

To use arp-scan in our case, we need to know the interface on the Ubuntu box, the MAC address of the device (Destination MAC), the vlan ID of the switch port and the ip network the device is on. 

For the vlan ID, we select one from the vlans configured on the switch. You can use show vlan brief to see a list of vlans assigned to ports. If the switch has a lot of vlans defined you may have to run the command several times, iterating through different vlans.

In this example:

Linux interface - enp2s0f1
vlan ID - 46 (10.112.46.0/23)
Device MAC – 00:90:9e:9a:b5:3d
Device IP – 10.112.100.1
Device Subnet - 10.112.100.0/24

As you can see in the diagram, the simulated device is on port g1/0/48 which is configured as an access port on vlan 46. The Linux box with arp-scan is on a trunk port. The requirement here is that the trunk can pass vlan tags on vlan 46. 

It doesn't matter if the trunk has a native vlan with DHCP. Security best practices dictates that the native vlan nk on a trunk be an unused vlan. For our purposes, we don’t care if the interface has an IP address since we are using arp. You will see in the output that the IP address on the interface isn’t set.

Interface configuration for the Ubuntu laptop

sh run int g1/0/47
interface GigabitEthernet1/0/47
 switchport trunk encapsulation dot1q
 switchport mode trunk
end

On theUbuntu laptop connected to port g1/0/47

ip addr show enp2s0f1

 
2: enp2s0f1: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc fq_codel state UP group default qlen 1000
    link/ether 80:fa:5b:31:de:85 brd ff:ff:ff:ff:ff:ff
    inet6 fe80::6d35:51a0:cef:4475/64 scope link noprefixroute
       valid_lft forever preferred_lft forever

You can see that it doesn't have an IP address.

Interface configuration for the simulated device

sh run int g1/0/48
interface GigabitEthernet1/0/48
 switchport access vlan 46
 switchport mode access
end

SVI Interfaces

sh run int vl 46
interface Vlan46
 ip address 10.112.47.254 255.255.254.0
 ip helper-address 192.168.10.221
  no ip redirects
end

sh run int vl 100
interface Vlan100
 ip address 10.112.100.254 255.255.255.0
 ip helper-address 192.168.10.221
 no ip redirects
end

Run arp-scan

sudo arp-scan -I enp2s0f1 -Q 46 --destaddr=00:90:9e:9a:b5:3d 10.112.100.0/24
WARNING: Could not obtain IP address for interface enp2s0f1. Using 0.0.0.0 for
the source address, which is probably not what you want.
Either configure enp2s0f1 with an IP address, or manually specify the address
with the --arpspa option.
Interface: enp2s0f1, datalink type: EN10MB (Ethernet)
Starting arp-scan 1.9 with 256 hosts (http://www.nta-monitor.com/tools/arp-scan/)
10.112.100.1    00:90:9e:9a:b5:3d    Critical IO, LLC (802.1Q VLAN=46)

1 packets received by filter, 0 packets dropped by kernel
Ending arp-scan 1.9: 256 hosts scanned in 2.556 seconds (100.16 hosts/sec). 1 responded

You can see that arp-scan found the device by mac address and the device replied with its IP address.

Here is what it looked like in Wireshark on the Ubuntu box:

You can see that arp-scan sent 802.1q tag 46 even though I hadn't configured a subinterface on the Ubuntu box. I have a blog showing how to configure Ubuntu to use vlan tags. Here is a link to the blog - Bypass VTY access lists with Linux and Yersinia

Now on the switch, look for the mac address. 

sh mac add | i 0090.9e9a.b53d   
  46    0090.9e9a.b53d    DYNAMIC     Gi1/0/48

You can either move the device to the correct port or reconfigure the port for the correct vlan. If the customer allows it, I like to label this type of device's switch port like this:

des < BACnet 10.112.100.1 0090.9e9a.b53d>

That gives me the MAC and IP for future troubleshooting. 

Let's set up a lab to learn how to use arp-scan.

It's a simple setup, but there are few gotcha's if you are new to Linux or arp-scan. You will need a Linux machine, physical or virtual, and a Kali Linux virtual machine. The Kali VM will simulate our OT device because it is designed to be quiet on the network. The kali motto is "The quieter you are, the more you can hear".

We will use the same network layout as above so you can refer to that diagram.

On the Kali VM

Configure Kali with a static ip address. In this example:

10.112.100.1/24
255.255.255.0
NO GATEWAY - If you assign a gateway the Kali box will send ARP requests to the gateway and populate the switch's mac address table.

Connect the Kali VM to switch port g1/0/48

Check to see if the Kali box sent traffic that caused the switch to record it's MAC address:

sh mac add int g1/0/48                                               
          Mac Address Table                                                    
-------------------------------------------                                    
                                                                               
Vlan    Mac Address       Type        Ports                                    
----    -----------       --------    -----                                    
  46    0090.9e9a.b53d    DYNAMIC     Gi1/0/48                                 
Total Mac Addresses for this criterion: 1               

Kali did send some traffic and that populated the mac address table. For our purposes, we need to make sure the Kali box isn't sending any traffic. Normally, you do not want your pen test box to send traffic you didn't explicitly request. That is why Kali has DHCP and other services disabled by default. 

In this case, I had been using DHCP before switching to static so the dhclient service was still running.

On Kali run

ps -ef | grep dh
root      2500  2125  0 13:18 pts/0    00:00:00 dhclient -v

If you see the dhclient service, then run
dhclient -r


to stop the service. If you don't stop it, the dhclient service will do a discover which will populate the MAC-address table on the switch and invalidates the test we are about to try.

Next, run the following to clear the mac address on the switch port. Sometimes you need to run it a few times before the address is cleared.

clear mac address-table dynamic interface g1/0/48

Finally, you should see an empty mac table for interface g1/0/48

sh mac add int g1/0/48                        
          Mac Address Table
-------------------------------------------

Vlan    Mac Address       Type        Ports
----    -----------       --------    -----

Try to ping the device

ping 10.112.100.1

Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 10.112.100.1, timeout is 2 seconds:
.....
Success rate is 0 percent (0/5)

Connect your laptop to port 1/0/47. I run the lldpd daemon (sudo apt install lldpd) so I can verify that the laptop is connected using the following.

sh lldp ne
Capability codes:
    (R) Router, (B) Bridge, (T) Telephone, (C) DOCSIS Cable Device
    (W) WLAN Access Point, (P) Repeater, (S) Station, (O) Other

Device ID           Local Intf     Hold-time  Capability      Port ID
PROCURVE J9450A     Gi1/1/4        120        B               2
1S1K-SYS76          Gi1/0/47       120        B,W,R           80fa.5b31.de85

Total entries displayed: 2

Look at the interface that the laptop is connected to:

sh run int g1/0/47

interface GigabitEthernet1/0/47
 switchport trunk encapsulation dot1q
 switchport mode trunk
end

Look at the interface on the laptop after it's connected to the switch

ip addr show enp2s0f1 

2: enp2s0f1: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc fq_codel state UP group default qlen 1000
    link/ether 80:fa:5b:31:de:85 brd ff:ff:ff:ff:ff:ff
    inet6 fe80::6d35:51a0:cef:4475/64 scope link noprefixroute
       valid_lft forever preferred_lft forever

You can see that the interface is UP/UP but doesn't have an IP address.

Look at the SVIs

sh run int vl 46

interface Vlan46
 ip address 10.112.47.254 255.255.254.0
 ip helper-address 192.168.10.221
 no ip redirects
end

sh run int vl 100

interface Vlan100
 ip address 10.112.100.254 255.255.255.0
 ip helper-address 192.168.10.221
 no ip redirects
end

Now we are ready to run arp-scan and find the device:

sudo arp-scan -I enp2s0f1 -Q 46 --destaddr=00:90:9e:9a:b5:3d 10.112.100.0/24

WARNING: Could not obtain IP address for interface enp2s0f1. Using 0.0.0.0 for
the source address, which is probably not what you want.
Either configure enp2s0f1 with an IP address, or manually specify the address
with the --arpspa option.
Interface: enp2s0f1, datalink type: EN10MB (Ethernet)
Starting arp-scan 1.9 with 256 hosts (http://www.nta-monitor.com/tools/arp-scan/)
10.112.100.1    00:90:9e:9a:b5:3d    Critical IO, LLC (802.1Q VLAN=46)

1 packets received by filter, 0 packets dropped by kernel
Ending arp-scan 1.9: 256 hosts scanned in 2.556 seconds (100.16 hosts/sec). 1 responded

Verify that the mac-address table on the switch has been updated

sh mac add | i 0090.9e9a.b53d   
  46    0090.9e9a.b53d    DYNAMIC     Gi1/0/48

Learning Python 3

Updated September 10th, 2022

Here are some of the resources I used to start learning python. With my newly learned  Python skills and some Google-Fu I have been able to automate several network device tasks. You can find most of my python scripts at Hubbard on Networking GitHub Repo.

You do NOT need to know anything about python to use the scripts. This is just like you don't have to know how to program to run "show interface g1/0/1". You simply download the script and execute it.

I found this tweet that has a curated list of python resources:

A curated list of Ultimate Python resources

Why You Should Learn Python

A lot of the tasks that network engineers perform are repetitive, mind-numbing, and error-prone. With a little python skill, you can automate these tasks and spend the time you save on more productive tasks, like learning more python.

As networking moves away from the CLI and into software-defined networking (SDN) you will need to have some dev skills. Cisco has a three-part video on how the network engineer's job is changing. You will need to register with Cisco Devnet to watch it but you should have a Devnet account if you going down this path:
Lesson 1: The Network Engineer of Old

If you have never used Python at all, this blog is the place to get started!

First, to install python, head over to the Python download page - Download Python
Follow the instructions to install python on your OS of choice.

Tools

There isn't much needed to use Python other than python itself but like most things, life is easier with some tools.

Integrated Development Environment (IDE)

IDEs are tools that allow you to write and debug code. Once you start writing scripts that are more than a few lines long you will want to use an IDE.

Thonny - Python IDE for beginners. A free Integrated Development Environment. This tool is great for learning. It lets you step through a script and see exactly what is happening.

MU - a simple Python editor for beginner programmers. This one is really nice. It's cross-platform and has support for Linux, Mac, Windows, and Raspian. What separates it from the other tools listed here is the support for small devices like Adafruit and Micro:bit. Here is a screenshot of MU starting up:

Microsoft Visual Studio Code - A free open source IDE from Microsoft. VSCode has turned into an amazing development environment and can be used for any size project. It has an integrated debugger that looks just like the Powershell ISE tool. It supports almost every programming language, not just python. The open-source version of PowerShell is fully supported which is great. I can use one tool and create Python and PowerShell scripts. 

There is a Visual Studio Marketplace with thousands of plugins, similar to the Chrome store or Firefox store. Extensions for the Visual Studio family of products

I have more detail on my macOS blog. Once you have VScode installed it works the same on Windows, Mac, and Linux so the blog is useful regardless of what OS you use. My VSCode install blog

Code Editor

You can definitely use VSCode as your editor. It has about every feature that you could want. But I have been using Sublime text since before VSCode came out and old habits die hard! If you are on Ubuntu 22.04 you can install Gnome Text Editor (I know, really, really stupid name) and it works great for quick editing.

Sublime text - Sublime is a text editor that is optimized for programming. It has a huge community around it and thousands of plugins. It's $75.00 but the license lets you run it on as many machines as you own. I bought it and installed it on my Linux, Windows, and Mac laptops. It has a tabbed interface like notepad++ which I like. You can also split the screen and open two files side by side. This is useful because you can have your script on one side and the data file on the other. 

Realpython.com sells a great tutorial that walks you through installing Sublime text optimized for Python. It includes video and text for Mac, Linux, and Windows. This tutorial is well worth the cost and has improved my productivity in Sublime.

In the next section, I discuss revision control with Git. Sublime text has several plugins that integrate Git into your workflow.  One I really like is Git Gutter. It puts a + sign next to lines that have changed, then you can revert easily if the change didn’t work.
Your Shortcut to a Professional Python Development Setup

Revision Control

Git - A revision control system. It's useful once you start writing scripts large enough to have bugs or future enhancements. Even if you don't program in python it's worth installing git because of github.com and gitlab.com.

Both of these sites have thousands of python tools. If you have git installed on your computer all you have to do to use them is "git clone <repository>". For example, to install the ARP sorting tool I wrote, you simply go to ARP-Sort and click the "Code" button. It will display the URL for the project. Click the copy button, type “git clone” and paste the URL you copied into the terminal, then press enter:

git clone https://github.com/rikosintie/ARP-Sort.git

This downloads the project and unzips it into the folder ARP-Sort.

Someone has created an online game for learning Git - An open source game about learning Git!

Install git from https://git-scm.com/
Pro Git book - A free online book on git
Learn Git Command with Practical Examples on Linux – Part 1

Cisco DevNet GitHub Repo - Great resources on setting up your laptop with Python, Git, Postman, etc.

Git and GitHub for Beginners - Crash Course - A really good video on git.
 

Videos from Udemy.com 

Udemy has inexpensive video training for Python, Linux, and a lot of other applications. These are on sale all the time for $9.99

• Python Network Programming - Part 1: Build 7 Python Apps
• Complete Python Bootcamp: Go from zero to hero in Python 3
• 100 Days of Code - The Complete Python Pro Bootcamp for 2021

Videos on Youtube

I find that I learn better when using books and websites but sometimes it's nice to watch a video.

Real python did a blog on the best Youtube channels for python
The Ultimate List of Python YouTube Channels

Subscribe to HackerSploit on Youtube and there is a complete series on Python. He uses 2.7 but it is still a good tutorial. They are really basic but I find Alexis entertaining.
Python For Ethical Hacking - #1 - Introduction & Python Modules

Telusko Python for Beginners
Python Tutorial - Python for Beginners [Full Course] - Mosh 
Learn Python - Full Course for Beginners [Tutorial] Free Code Camp

Python Tutorial For Beginners (With Notes) - Code with Harry

Python Tutorial for Beginners 1: Install and Setup for Mac and Windows - Corey Schafer

Python Engineer

Writing Pythonic Code - A Tweet thread by @Bascodes. He is worth following.

A Beginner's Guide to CI/CD Pipeline Network Automation with Docker, Github and Python

Corey Shafer Videos

I recommend that you subscribe to this channel. Here are four of his videos that I found very useful

Requests Tutorial - The requests library is used to pull data down from webservers

JSON Tutorial - Java Script Object Notation is a common data format used by APIs

Sorting Tutorial - Sorting routines for lists and dictionaries

List Comprehensions - Working with list comprehensions

e-books from Amazon  

I love the Kindle app on my laptop, phone and iPad. If I get stuck in a long line I just open it up and do some studying! These were all under $5. You can go to Amazon, set filter to Kindle store and enter "python programming free book" and find a lot of free books.

• Learn Python in One Day and Learn It Well Python for Beginners with Hands-on Project The only book you need to start coding in Python immediately By Jamie Chan
• Python Tips and Tricks: Learn the Best Tips and Tricks to Get The Most out of Python NOW! Jones, Daniel
• The Fundamentals Of Python Programming: A Complete Beginners Guide To Python Mastery.
• Python Programming Tips and Tricks: The Ultimate Cheat Sheet for Python Programming. 20+ Tips and Tricks to Make Your Life Easier and More Efficient
• Automate the Boring Stuff with Python: Practical Programming for Total Beginners

Websites

There are so many python websites it would be impossible to list them all, here are a few I have found very useful:

Getting Started

• realpython.com - A great site for learning python. You can sign up for a weekly tip that is emailed. They also have a lot of tutorials that are very good.
• Real Python Your Guide to the Python print() Function - Includes using f strings. Very good tutorial.
  
• realpython.com/start-here/ - This page has a lot of getting started tips.
• realpython.com/products/real-python-course/#course-packages - This is a $60 course that looks pretty comprehensive. I didn't take it but everything else from real python has been good.
• Tutorials Point - Python 3 tutorials
• Python Practice website - A free site with practice problems and solutions.
• Python for Beginners
• Geeks for Geeks - A computer science portal for geeks. Search for python.
• What I did to learn Python
• Finxter Python Courses - This site has training and if you register free cheat sheets.
• A Quick Tour of Python Language Syntax - by Jake VanderPlas. Much more on this site.
• String Manipulation and Regular Expressions- by Jake VanderPlas. Much more on this site.
• Stack Overflow - A site dedicated to programming questions
• 17 Killer GitHub Repos You Need to Save Right Now! - Not 100% python, but a lot of resources.
  

General Tips

• Grepper - An awesome collection of code. They have a Chrome extension that captures code searches and displays ranked results. Pretty cool.
• Python 3 Module of the Week - A site with a ton of examples of how to do things in python. There is a good tutorial on the IP Address libraries.
• Python Built In Functions
  
• Understanding all of Python, through its builtins
• Python parentheses primer
• Python, argparse, and command line arguments
• Python Utilities
• Reverse Strings in Python: reversed(), Slicing, and More
  
• Python Regex Cheatsheet
• Data Science Cheat Sheet - Python Regular Expressions
• ActiveState Code Recipes - Welcome to the ActiveState code recipes repo! We have migrated all of the great content from code.activestate.com to its new forever-home here at GitHub. This makes it easier for everyone to submit new recipes, contribute code and integrate all the great information into their own projects.
• 10 Python Scripts to Automate Your Daily Problems
  
• Documenting Python Code and Projects
  

Jinja Templates

• Template Designer Documentation - Jinja is a templating language that you can use with Python
• Python for Network Engineers Jinja tutorial
• Tips and Tricks
• Getting started with Jinja2
• List of Control Structures
• jinja2-live-parser
• Pallet Projects Jinja Tutorial
• Jinja2 configuration templates - Python for Network Engineers

Network Engineering

• Hubbard On Networking GitHub Repo
  
• Python for Network Engineers - The name says it all! Kirk Byers wrote the netmiko python libray to automate network device operations.
• Netmiko Github - The github repository for netmiko python library
• Cisco Devnet site - The learning labs part of DevNet. Great training videos. You can use a Cisco account or create a free account.
• Cisco DevNet Evolving Technologies Study Guide - Nick Russo's guide
  
• Batfish - An Open Source network configuration analysis tool
  
• Cisco Config Analysis Tool - A python tool that takes a Cisco running config and compares it to the Cisco best practices guide.
• Primer on Jinja Templating - Jinja templates can be used to create config files from Excel data.
  
• Welcome to the Postman docs! - Postman is a tool used to interact with RESTful API. 
  
• Reading and Writing CSV Files in Python
  
• Getting started with TextFSM
  
• Example of using Jinja - Python for Network Engineers
  

Debugging

• Python 3 - Exceptions Handling
  
• Python Try Except Else Finally error handling
  
• Tips for debugging with print()

Web Development

• Twitter University is Free! - You can learn 98% of web development by reading these 10 threads
• Awesome Web Development Resources - Not specifically Python but has a lot of great resources
• Create Web Apps with Python Flask
  

Style guides

Python is a structured language that uses white space as part of the structure. But you can still create ugly code. The official Python style guide is part of the Python Enhancement Proposals (PEPs) which are documents that provide guidance and spell out best practices for how Python code should be organized, packaged, released, deprecated, and so on. PEP8 is a popular standard for styling Python code and is extensively used in the developer community. 

• PEP 8 – Style Guide for Python Code - The official style guide for Python
• How to Write Beautiful Python Code With PEP 8 - Real Python PEP8 Tutorial
  
• Documenting Python Code: A Complete Guide

Python Virtual Environments

As you start learning and creating more python tools you will want to start using virtual environments. These two blogs will teach you what you need to know. There are a lot more blogs available on the Internet.

• Python Virtual Environments: A Primer
• Managing Multiple Python Versions With pyenv
• Modern Python Environments - dependency and workspace management

Podcasts

You probably won't learn much coding from a podcast but these are very interesting to listen to. I find a lot of good links in the show notes. For example, I learned about Thonny, MU, and Visual Studio Code from podcasts.
Talk Python To Me - A good podcast that covers a lot of topics. There will be one called "Teaching Python to network engineers" in August, 2018!
Podcast.__init__ - A podcast about Python and the people who make it great. Hosted by Tobias Macey.
Python Bytes - Python Bytes podcast delivers headlines directly to your earbuds. If you want to stay up on the Python developer news but don’t have time to scour Reddit, Twitter, and other news sources, just subscribe and you’ll get the best picks delivered weekly.

Keywords In Python

There are 33 keywords that should never be used as a variable, function name, class, object, or as any other identifiers in your programs.

 false
 True
 finally
 class
 for
 continue
 none
 return
 lambda
 try
 is
 def
 from
 nonlocal
 while
 and
 not
 global
 del
 with
 as
 elif
 if
 or
yield
 break
 import
 except
 pass
 assert
 else
 raise
 in

Libraries

Pint - Pint is a Python package to define, operate and manipulate physical quantities