13 Apr

Use Ansible to check SNMP on remote device

Best way to learn Ansible and the whole idea of automation is to start from the small playbooks and then grow big. If you first automate simple tasks, even those that may be easier and quicker to perform from the command line, you will learn how Ansible is working. Let’s say, we want to test if SNMP is responding on the remote host (we name it HostA). We will use SNMPv3 and authPriv security model. And of course, we want to write the Ansible playbook and run it on server HostNOC.

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23 Nov

Dynamic VIRL inventory for Ansible playbooks

Ansible is one of the powerful tools providing us an automation of recurring tasks. In the current world, it is impossible to manage infrastructure manually efficiently. Many people still do this but the world has already changed and we need to progress otherwise our business will be cost ineffective. You can provide static inventory – list of the devices where you want to execute the playbook. But in dynamic environments, such as Cisco VIRL simulations you don’t want to edit inventory file manually. That is why I use Python script that will generate Dynamic VIRL inventory for Ansible playbook for me.

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05 Sep

AWS Step Functions for networkers – the CLI approach

Step Function Workflow Graph

In the previous post, I told you that it is not possible to update State Machine configuration once you create it. I prefer an approach like in API Gateway where you have stages of the same project, but Amazon for some reason did not follow this way. So if you want to deploy a new version of your Step Functions project you need to delete old and create new State Machine. Using the GUI interface is not efficient in a long term, you can do this much easier using AWS CLI.

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30 Aug

AWS Step Functions for networkers – Workflow definition

Step Function Workflow Graph

AWS has many great tools and products that may simplify your task. In day to day work, no matter if you are networks engineer, software administrator or have a different role in your organization you will perform small repetitive tasks to complete the bigger project. Writing a long, complex scripts or programs is a solution, but it is flexible? Step Functions is a good option in such cases.

Good programming rule is to create small functions to complete small chunk of work and then pass it on another one. So instead of writing one script that will log into 100 devices to fetch firmware version you create a small function that does it for one device and then you call it in a loop in other function passing the new IP as an argument. That is exactly what AWS Step Functions are meant for. Using this service you can create a flow of small tasks, each dependent on other if required, to complete bigger work. Let me show you the basics and how you can use it.

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28 Jul

AWS Lambda guide part IV – API Gateway and Lambda without S3

AWS Lambda Tutorial, I will show you how to create or import your Python application to Lambda, use S3 bucket, add S3 trigger for Lambda and more!

It is time for some new final tuning of my small certificate signing service. In previous parts, I showed you what AWS Lambda service is and how to import simple Python application into serverless microservice. I also connected Lambda function to S3 storage service where I put certificates and key files. Then I added a trigger to the function, so Lambda function will execute automatically every time someone uploads new CSR file with certificate request to S3 bucket. Now I will show you not only how to make this function serverless but also storageless using API Gateway. It is not standard approach but in some scenarios might be interesting. So we will connect API Gateway and Lambda without S3 backend for keys and certificates.

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07 Jul

How to display HTML page using only AWS API Gateway

API Gateway is a powerful tool you can use to create a frontend for your application hosted on AWS. It let developers create, maintain, secure and monitor API on a large scale. This API is a gateway to access your data, functions, logic or any web application hosted on AWS. Logic is based on RESTful API framework used in an example by web servers and can be used to eliminate physical or virtual servers from infrastructure. API Gateway is a tool for a dynamic and flexible approach for data transformation. Let me show you how to display HTML page using only AWS API Gateway.

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04 Jul

AWS Lambda guide part III – Adding S3 trigger in Lambda function

AWS Lambda Tutorial, I will show you how to create or import your Python application to Lambda, use S3 bucket, add S3 trigger for Lambda and more!

This is third part of the tutorial of AWS Lambda. In previous chapters I presented my small Python app I created for signing certificate requests and imported it to AWS Lambda service (check AWS Lambda guide part I – Import your Python application to Lambda). Then I modified the code so instead of using reference to static local files we can read and write to S3 bucket (check AWS Lambda guide part II – Access to S3 service from Lambda function). Now let’s move forward and add S3 trigger in Lambda function.

We can always execute Lambda function manually either from web panel or using CLI. We can also execute it from our other application if required. But microservices are often triggered by events. In this article I will show you how to automatically sign certificate using my Lambda function when request file is uploaded to S3 bucket. Let me show you how to program S3 trigger in Lambda.

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26 Jun

AWS Lambda guide part II – Access to S3 service from Lambda function

AWS Lambda Tutorial, I will show you how to create or import your Python application to Lambda, use S3 bucket, add S3 trigger for Lambda and more!

In previous chapter I talked a little what is AWS Lambda and idea behind serverless computing. Furthermore I presented small Python application I wrote to sign certificate requests using my CA authority certificate (how to create such you can find in my post How to act as your own local CA and sign certificate request from ASA). Then after importing the sandboxed Python environment (required because of non-standard library used for SSL, whole procedure is described in my post How to create Python sandbox archive for AWS Lambda) and small change in the code we managed to execute it in Lambda. Also I mentioned that we can use other AWS services in our code, in example Access to S3 service from Lambda.

As you remember the initial version of my application have static paths to all files and assume that it can open it from folders on local hard drive. If you run function in Lambda you need a place where you can store files. This place is AWS S3. In this chapter I show you how to use S3 service in function on Lambda. We will use boto3 library that you can locally install on your computer using pip.

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15 Jun

AWS Lambda guide part I – Import your Python application to Lambda

AWS Lambda Tutorial, I will show you how to create or import your Python application to Lambda, use S3 bucket, add S3 trigger for Lambda and more!

I lately started playing with AWS Lambda for few reasons. I become interested in serverless architecture, ways to save money while running apps and I wanted finally to learn Python. I’m a network engineer, not a software developer. I like cloud computing and see it as important part of market now. So that was an opportunity for me to learn something new. Now I want to share my knowledge with you and show you how to import your Python application to Lambda.

In my tutorial I want to show you that Lambda and programming is something interesting that you can use for everyday work whatever you do. Of course Lambda tutorials are already available on Internet but they show you how to make new application from scratch. I want to show you how to import your own small Python application to Lambda, required changes to the code, python environment, testing approach and finally how to expand it using other AWS services. This post is just first chapter!

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