Nornir Network Automation

Nornir Network Automation

Nornir is a Python library designed for Network Automation tasks. It enables Network Engineers to use Python to manage and automate their network devices. Unlike tools like Ansible which rely on domain-specific languages, Nornir leverages the full power of Python, giving you more flexibility and control over your automation scripts.

Nornir feels like what you'd get if Ansible and Python had a baby. If you're used to Ansible, you know that you first set up your inventory, write tasks, and execute them on all or selected devices concurrently. Nornir operates similarly, but the big difference is you use Python code instead of any Domain Specific Language.

My Life Without Nornir

Before I discovered Nornir, my approach to Python automation involved manually setting up a list of devices, specifying each one's vendor, and credentials. This setup could be a simple Python list or a dictionary. Then, I'd loop through each device with a for loop, using libraries like Netmiko or Napalm to execute tasks. These tasks ranged from getting data from the devices to sending configurations. Here is a very simple snippet of managing the devices and using them with Netmiko. This method can get complicated very easily once you start Continue reading

Repost: EBGP-Mostly Service Provider Network

Daryll Swer left a long comment describing how he designed a Service Provider network running in numerous private autonomous systems. While I might not agree with everything he wrote, it’s an interesting idea and conceptually pretty similar to what we did 25 years ago (IBGP without IGP, running across physical interfaces, with every router being a route-reflector client of every other router), or how some very large networks were using BGP confederations.

Just remember (as someone from Cisco TAC told me in those days) that “you might be the only one in the world doing it and might hit bugs no one has seen before.”

Read more …

Repost: EBGP-Mostly Service Provider Network

Daryll Swer left a long comment describing how he designed a Service Provider network running in numerous private autonomous systems. While I might not agree with everything he wrote, it’s an interesting idea and conceptually pretty similar to what we did 25 years ago (IBGP without IGP, running across physical interfaces, with every router being a route-reflector client of every other router), or how some very large networks were using BGP confederations.

Just remember (as someone from Cisco TAC told me in those days) that “you might be the only one in the world doing it and might hit bugs no one has seen before.”

Read more …

HN727: Kubernetes Networking Essentials

Where there are containers, there is networking. Today we dig into the networking that underlies Kubernetes, the open source orchestration platform for container-based applications. Our guest Karim El Jamali takes us through the essential concepts: Nodes, pods, clusters, CNIs, virtual ethernet pairs, ingress controller, eBPF, and service meshes. As container-based applications grow in popularity, it’s... Read more »

Copilot Not Autopilot

I’ve noticed a trend recently with a lot of AI-related features being added to software. They’re being branded as “copilot” solutions. Yes, Microsoft Copilot was the first to use the name and the rest are just trying to jump in on the brand recognition, much like using “GPT” last year. The word “copilot” is so generic that it’s unlikely to be to be trademarked without adding more, like the company name or some other unique term. That made me wonder if the goal of using that term was simply to cash in on brand recognition or if there was more to it.

No Hands

Did you know that an airplane can land entirely unassisted? It’s true. It’s a feature commonly called Auto Land and it does exactly what it says. It uses the airports Instrument Landing System (ILS) to land automatically. Pilots rarely use it because of a variety of factors, including the need for minute last-minute adjustments during a very stressful part of the flight as well as the equipment requirements, such as a fairly modern ILS system. That doesn’t even mention that use of Auto Land snarls airport traffic because of the need to hold other planes outside Continue reading

Use AGW for packet radio applications

When creating packet radio applications, there are several options on how to get the packets “out there”, and get them back. That is, how to interface with the modem.

Sure, you can write your own modem, and have the interface to the outside world be plain audio and PTT (push to talk, i.e. trigger transmit). But now you’re writing a modem, not an application. You should probably split the two, and have an interface between them.

KISS

You can use KISS, but it’s very limited. You can only send individual packets, so it’s only really good for sending unconnected (think UDP) packets like APRS. It’s not good for querying metadata, such as port information and outstanding transmit queue.

Think of KISS like a lower layer that applications shouldn’t think about. Like ethernet. Sure, as a good engineer you should know about KISS, but it’s not what your application should be interfacing with.

Linux kernel implementation

On Linux you can use AF_AX25 sockets, and program exactly like you do for regular internet/IP programs. SOCK_DGRAM for UI frames (UDP-like), and SOCK_STREAM for connected mode (TCP-like).

But the Linux kernel implementation is way too buggy. SOCK_STREAM works kinda OK, but does Continue reading

1000BASE-T Part 1 – Introduction

How does Ethernet detect that a link goes down? This, what I thought was a simple question, I asked myself a couple of weeks ago. I realized I didn’t have a very good answer. I realized I had more to learn about Ethernet and the physical layer and so does pretty much the entire networking industry. Through the graceful help of Peter Jones at Cisco, I got in touch with George Zimmerman, an independent professional with a PhD in electrical engineering, a history of teaching at Caltech, and that works within the IEEE on different standards. To answer my initial question, we first need to understand more about Ethernet, and especially the physical layer. As every version of Ethernet has slightly different PHY, I will be covering 1000BASE-T. This will be covered in a series of posts, this being the first.

Going back to the OSI model, most roles in networking puts the focus on layers two to four:

This is natural as most of our work relates to these layers.

When we think of two hosts communicating, we imagine that the transceivers connect to each other and that there are ones and zeroes traveling across the cable:

Continue reading

On the ‘net: Networking Models

I’m writing a series on network models over at Packet Pushers; links to the first three are below.

Looking back at my career in network engineering, beyond some basic concepts and naming conventions, I cannot remember using the OSI model once. I have used the concept of layering, but never the OSI model specifically.

First, models are not sacrosanct. A model is just a tool. If the model you are using is not working for you, feel free to modify it. I find simpler yet extensible models far more effective than complex models for channeling my thoughts. In the past I have tried building huge models that “put everything in one place,” but they do not work for me.

How does a host differ from a middlebox? Hosts are designed to run applications that create and consume packets rather than quickly forwarding traffic through the network. The primary difference is that the source and destination are not two different ports on the same device but rather a virtual interface representing an application and a physical interface.

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