Encapsulation of PDUs On Trunk Ports

When I studied for my CCIE almost 15 years ago, I recall that I was fascinated by how different PDUs such as CDP, DTP, STP would have different encapsulations on a trunk depending on the configuration of it. What happens when you change the native VLAN? What happens if the native VLAN is not allowed on the trunk? What happens if you tag the native VLAN? There aren’t many resources describing this as most people don’t care for this level of detail, but there are situations where this is important. The goal of this post is to configure different protocols and see how they are encapsulated using different trunk configurations. You don’t need to consume this entire post, rather use it as a reference for different scenarios. Just be aware that some of this may be platform/OS specific.

The protocols we’ll cover for this post are:

  • CDP.
  • LLDP.
  • DTP.
  • PAgP.
  • LACP.
  • PVST+.
  • RPVST+.
  • MST.

The topology is going to be very simple, two switches connected by a single link:

These are IOSv-L2 devices:

SW1#show version
Cisco IOS Software, vios_l2 Software (vios_l2-ADVENTERPRISEK9-M), Experimental Version 15.2(20200924:215240) [sweickge-sep24-2020-l2iol-release 135]
Copyright (c) 1986-2020 by Cisco Systems, Inc.
Compiled Tue 29-Sep-20 11:53 by sweickge


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Torero – Boots on the Ground Framework for Automation Sharing

Background One of the many useful things I came away with from AutoCon1 in Amsterdam was a "to-do" to investigate torero. Launched by Itential at NAF's AutoCon1 as a community based product and presented to the AutoCon community by Peter Sprygada in Amsterdam, one has to take notice and I did. You can see Mr. READ MORE

The post Torero – Boots on the Ground Framework for Automation Sharing appeared first on The Gratuitous Arp.

Ongoing Saga: How Much Money Will Be Spent On AI Chips?

Everybody knows that companies, particularly hyperscalers and cloud builders but now increasingly enterprises hoping to leverage generative AI, are spending giant round bales of money on AI accelerators and related chips to create AI training and inference clusters. …

Ongoing Saga: How Much Money Will Be Spent On AI Chips? was written by Timothy Prickett Morgan at The Next Platform.

Using a Git Commit Template

Although I’m sure that I’d seen or read about Git commit templates previously, the idea of using a Git commit template was brought to the forefront recently with the release of version 11 of Tower for Mac. When I’m using macOS, Tower is my graphical Git client of choice. However, most of my Git operations are via the terminal, and I’m not always using macOS (I also spend a fair amount of time using Linux). For that reason, I wanted to implement a more “platform-neutral” solution to Git commit templates. In this post, I’ll share with you what I learned about using a Git commit template.

Let me start with explaining why I wanted to start using a Git commit template. Some time ago, I was exposed to the Conventional Commits specification, and decided I wanted to adopt this for my personal projects. As with starting any new habit, it can be challenging to remember, and I found myself committing changes to personal repositories without following the specification. So when I was reminded of Git commit template functionality via its inclusion in Tower, I immediately realized this would be a great way to help build new habits (and Continue reading

Adding Arista Switch to CML

I wanted to add Arista switches to CML to do some STP interopability testing. However, the process of adding them is not well described. I had to refer to some Youtube videos to understand what to do. This is what you’ll need for CML 2.7:

  • Download images from Arista software downloads.
  • Upload images to CML.
  • Create node- and image definition.

The first thing you need to do is to download images. Thankfully, Arista provides images for anyone that’s registered, whether you are an existing partner/customer, or not. Go to Arista’s login page and create an account if you don’t already have one. When logged in, go to Support -> Software Download:

When on the downloads page, scroll down until you see cEOS-lab and vEOS-lab. Expand the vEOS lab section:

You will need to download two images:

  • Aboot – Boot loader.
  • vEOS – The actual NOS.

Grab one of the Aboot images such as Aboot-veos-serial-8.0.2.ios:

The Aboot serial image outputs to serial while the other image outputs to VGA. I didn’t have any issues using the serial one in CML.

You’ll then need the actual vEOS file. Previously, there was a process needed to convert Continue reading

Worth Reading: GitHub Copilot Workspace Review

In Matt Duggan’s blog post, you’ll find a scathing review of another attempt to throw AI spaghetti at the wall to see if they stick: the GitHub Copilot Workspace.

He also succinctly summarized everything I ever wanted to say about the idea of using AI tools to generate networking configurations:

Having a tool that makes stuff that looks right but ends up broken is worse than not having the tool at all.

DNS Evolution

The choice of UDP as the default transport for the DNS was not a completely unqualified success. On the positive side, the stateless query/response model of UDP has been a good fit to the stateless query/response model of DNS transactions between a client and a server. On the other hand, these same minimal overheads imply that DNS over UDP cannot perform prompt detection of packet loss and cannot efficiently defend itself against various approaches to tampering with the DNS, such as source address spoofing, payload alteration and third-party packet injection. Perhaps most importantly, the way UDP handles large payloads is a problem.

Weekend Reads 071224


The gang’s time from initial access to draining data out of a Veeam server is shockingly fast; after which the attackers went on to deploy actual ransomware in less than a day.


A critical security issue has been disclosed in the Exim mail transfer agent that could enable threat actors to deliver malicious attachments to target users’ inboxes.


The new fireball is the arrival of AI, its widespread acceptance and adoption, and the view that it is now a competitive imperative.


As a follow-up to the post yesterday on native VLANs, there was a question on what would happen to 802.1Q-tagged frames traversing an unmanaged switch.


State-controlled media on Tuesday covered the proceedings of the third China IPv6 Innovation and Development Conference, at which officials revealed that as of May 2024 the Middle Kingdom was home to 794 million users of the protocol, and that 64.56 percent of mobile traffic – plus 21.21 percent of fixed network traffic – is carried on networks that employ it.


In fact, since 2017, Google’s environmental reports show that the company’s electricity use, CO2 emissions, and carbon intensity have soared.


Using DevSecOps helps ensure the right level of security throughout both Continue reading

Terraform for Network Engineers: Part Three

Terraform for Network Engineers: Part Three

If you have not read the previous parts of this series, I recommend you start there.

Terraform for Network Engineers: Part One
Terraform for Network Engineers: Part Two

Welcome back to our journey of exploring Terraform for Network Engineers. In the previous part, we left ourself with a few challenges network engineers face when diving into the world of Terraform. Let's quickly recap those challenges:

  1. Setup Complexity: Are we really expecting network engineers to set up a Terraform project and write HCL code for creating resources on Panorama?
  2. Documentation Dive: Are network engineers supposed to dig into Terraform provider documentation to configure their desired resources?
  3. State File Management: What do we do with the state file? How do we manage it and share it with the team? What if it gets corrupted?

In this part, we'll tackle the first two challenges. We will explore how we can simplify the configuration file and abstract the complexity of the Terraform provider documentation.

Before we dive in, lets decompose the components of a simple Palo Alto Networks security policy configuration. A simple policy is composed of the following components:

  1. Device Group
  2. Source and Destination Zones
  3. Source and Destination Addresses
  4. Services Continue reading

IPB155: Operational Considerations: DHCP vs DHCPv6

What are the operational considerations and differences between DHCP and DHCPv6?  In today’s episode we explore the implications for network management, security, and operational models. We also discuss the challenges of DHCPv6 failover, high availability, complex device tracking and identity management in various environments. Episode Links:  Scott’s Infoblox IPv6 CoE blog post  Introducing DHCPv6 Prefix... Read more »

Application Security report: 2024 update

Over the last twelve months, the Internet security landscape has changed dramatically. Geopolitical uncertainty, coupled with an active 2024 voting season in many countries across the world, has led to a substantial increase in malicious traffic activity across the Internet. In this report, we take a look at Cloudflare’s perspective on Internet application security.

This report is the fourth edition of our Application Security Report and is an official update to our Q2 2023 report. New in this report is a section focused on client-side security within the context of web applications.

Throughout the report we discuss various insights. From a global standpoint, mitigated traffic across the whole network now averages 7%, and WAF and Bot mitigations are the source of over half of that. While DDoS attacks remain the number one attack vector used against web applications, targeted CVE attacks are also worth keeping an eye on, as we have seen exploits as fast as 22 minutes after a proof of concept was released.

Focusing on bots, about a third of all traffic we observe is automated, and of that, the vast majority (93%) is not generated by bots in Cloudflare’s verified list and is potentially malicious.

API traffic Continue reading

Euro 2024’s impact on Internet traffic: a closer look at finalists Spain and England

National team sports unite countries, and football (known as “soccer” in the US) is the world’s most popular sport, boasting approximately 3.5 billion fans globally. The UEFA Euro 2024, running from June 14 to July 14, 2024, significantly impacts Internet traffic across participating European nations. This blog post focuses on the two finalists, Spain and England, and comes after an initial post we published during the first week of the tournament.

Analyzing traffic patterns reveals distinct high-level trends. Spain saw the most significant drops in Internet traffic during games against major teams and former champions such as Italy (the defending champion), Germany, and France. In contrast, England’s games had crucial moments towards the end, leading to the largest traffic reductions in the UK, especially during the knockout stages.

For context, as previously mentioned, football games like the Super Bowl, differ from other events such as elections. When major teams or national squads play, especially in matches that captivate many viewers, Internet traffic often drops. This is particularly true if the game is broadcast on a national TV channel. During such broadcasts, people tend to focus more on their TV sets, relying on the traditional broadcast signal Continue reading

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