Multicast PIM Auto RP (V)

Multicast PIM Auto RP (V)

In the previous posts in this series, we covered the basics of multicast, IGMP, PIM Dense Mode, and PIM Sparse Mode. In the Sparse Mode post, we manually configured the RP address on every router in the network. This works fine in a small lab, but in a larger network with many routers, it becomes difficult to manage. If the RP changes, you have to update the configuration on every single router.

Multicast PIM Sparse Mode
Sparse Mode only sends traffic to parts of the network that explicitly request it. Routers with interested receivers send Join messages toward
Multicast PIM Auto RP (V)PacketswitchSuresh Vinasiththamby
Multicast PIM Auto RP (V)

AutoRP solves this problem by allowing routers to dynamically learn the RP address. Instead of manually configuring the RP on each router, you configure one or more routers to announce themselves as Candidate RPs. A separate router (or the same as the Candidate RP router) called the Mapping Agent collects these announcements and distributes the RP information to all other routers in the network. This makes RP management much easier and also provides a way to implement RP redundancy.

There are two methods to dynamically learn the RP address, which are Auto-RP and Bootstrap Router (BSR). In this Continue reading

Open-Source Network Simulators (2026 Edition)

Brian Linkletter published an updated overview of open-source network simulators and emulators.

containerlab and GNS3 are clear leaders (no surprise there) with the original vrnetlab becoming abandonware (fortunately, we have Roman Dodin’s fork), which makes me think we should focus on using netlab primarily with containerlab and slowly sunset the Vagrant support, particularly considering some people actively hate the license change.

Also, if anyone feels like writing an interface (provider module) between netlab and GNS3, the pull request would be most welcome 😎

Any thoughts? Please leave a comment!

Datacenter Spending Forecast Revised Upwards – Yet Again

This is turning into a “dog bites man” story, but the forecasts for spending in the datacenter for this year keep going up and up, and a few days ago Gartner’s economists and prognosticators finished up their tea and looked at the leaves at the common of a cup through a polished crystal ball and predicted that datacenter spending this year would go up. …

Datacenter Spending Forecast Revised Upwards – Yet Again was written by Timothy Prickett Morgan at The Next Platform.

NB561: Kubernetes Retires Ingress NGINX; Are Data Centers Headed for Orbit?

Take a Network Break! We start with a trio of follow-ups, including a correction regarding Mplify certifications, Cisco proposing new OSI layers, and free-space optics. Our Red Alert sounds off about a remote code execution vulnerability in the Ivanti Endpoint Manager Mobile agent. On the news front, Broadcom announces new silicon for wireless APs for... Read more »

Fast Arista cEOS Container Configuration

After the enormous speedup I achieved with the FRR containers, I tried to do something similar with the Arista cEOS ones. After all, Arista’s pretty open about running its software on standard Linux, so it should be possible to map host-side configuration files into container-side scripts and execute them, right?

There was just one tiny gotcha: all netlab-generated EOS configuration files are device configuration snippets that are intended to be submitted via EOS CLI, and I didn’t feel like cracking open the netmiko documentation (that’s another backburner project).

However, Arista cEOS includes this magic command called FastCli ;)

Read more …

Fragments of an adolescent web

I have unearthed a few old articles typed during my adolescence, between 1996 and 1998. Unremarkable at the time, these pages now compose, three decades later, the chronicle of a vanished era.1

The word “blog” does not exist yet. Wikipedia remains to come. Google has not been born. AltaVista reigns over searches, while already struggling to embrace the nascent immensity of the web2. To meet someone, you had to agree in advance and prepare your route on paper maps. 🗺️

The web is taking off. The CSS specification has just emerged, HTML tables still serve for page layout. Cookies and advertising banners are making their appearance. Pages are adorned with music and videos, forcing browsers to arm themselves with plugins. Netscape Navigator sits on 86% of the territory, but Windows 95 now bundles Internet Explorer to quickly catch up. Facing this offensive, Netscape opensource its browser.

France falls behind. Outside universities, Internet access remains expensive and laborious. Minitel still reigns, offering phone directory, train tickets, remote shopping. This was not yet possible with the Internet: buying a CD online was a pipe dream. Encryption suffers from inappropriate regulation: the DES algorithm is capped at 40 bits and Continue reading

Multicast PIM Sparse Mode (IV)

Multicast PIM Sparse Mode (IV)

In the previous post, we covered PIM Dense Mode and mentioned that it is not widely used in production because of its flood and prune behaviour. Every router in the network receives the multicast traffic first, and then routers without interested receivers have to send prune messages. This is inefficient, especially in large networks.

Multicast PIM Dense Mode
PIM Dense mode assumes that every subnet in the network has interested receivers, so it floods multicast traffic everywhere first. Routers that
Multicast PIM Sparse Mode (IV)PacketswitchSuresh Vinasiththamby
Multicast PIM Sparse Mode (IV)

In this post, we will look at PIM Sparse Mode, which takes the opposite approach. Instead of flooding traffic everywhere and pruning where it is not needed, Sparse Mode only sends traffic to parts of the network that explicitly request it. Routers with interested receivers send Join messages and only then does the multicast traffic start flowing. This makes Sparse Mode much more efficient and scalable, which is why it is the preferred mode in most production networks today.

PIM Spare Mode Overview

In Dense Mode, we saw two main problems. Multicast traffic is flooded everywhere, and every router has to maintain state for every multicast group, even if all its interfaces are pruned. Sparse Mode Continue reading

HN813: What Should Networkers Know About Software Development (and Vice Versa)?

What should network engineers know about software development? What should software developers know about networking? Ethan and Drew sit down with Chris Rapier and Nick Buraglio to discuss why crossing these silos can improve outcomes for everyone. They break down why being a little curious about the infrastructure can help software developers write better code,... Read more »

How Homepage simplifies monitoring your self-hosted services

Slowly but surely, I’ve been migrating over to self-hosted services so I can finally cut the cord to third parties. By keeping things within my LAN, I enjoy more security and privacy than I would if I continued using cloud hosts. The problem is, I wind up with a lot of different services running that I have to then access via different IP addresses and ports. But what if I wanted to simply (and quickly) view the status of those services, take a gander at statistics, or even confirm that my Docker containers are still running as expected? Do I open a browser tab for each of those to verify things are as expected? I could. Or, I could make use of a single dashboard that gives me all the information I need from a centralized location.

Technology Short Take 190

Welcome to Technology Short Take #190! This is the first Tech Short Take of 2026, and it has been nearly three months (wow!) since the last one. I can’t argue that I fell off the blogging bandwagon over the end of 2025 and early 2026. I won’t get into all the reasons why (if you’re interested then feel free to reach out and I’ll fill you in). Enough about me—let’s get to the technical content! Here’s hoping you find something useful.

Networking

Servers/Hardware

Security

Cloud Computing/Cloud Management

Lab: Routing Between VXLAN Segments

In the previous EVPN/VXLAN lab exercises, we covered the basics of Ethernet bridging over VXLAN and the use of the EVPN control plane to build layer-2 segments.

It’s time to move up the protocol stack. Let’s see how you can route between VXLAN segments, this time using unique unicast IP addresses on the layer-3 switches.

Explore the lab exercise

You can run the lab on your own netlab-enabled infrastructure (more details), but also within a free GitHub Codespace or even on your Apple-silicon Mac (installation, using Arista cEOS container, using VXLAN/EVPN labs).

Hedge 294: Resource Constrained Environments


 
The future of network design and architecture is–based on current trends–is going to be working with and around resource constraints. How would resource constraints impact the way we design and manage networks? Mike Bushong joins Tom, Eyvonne, and Russ to ponder network engineering in a resource constrained world.
 

 
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Migrating from NGINX Ingress to Calico Ingress Gateway: A Step-by-Step Guide

From Ingress NGINX to Calico Ingress Gateway

In our previous post, we addressed the most common questions platform teams are asking as they prepare for the retirement of the NGINX Ingress Controller. With the March 2026 deadline fast approaching, this guide provides a hands-on, step-by-step walkthrough for migrating to the Kubernetes Gateway API using Calico Ingress Gateway. You will learn how to translate NGINX annotations into HTTPRoute rules, run both models side by side, and safely cut over live traffic.

A Brief History

The announced retirement of the NGINX Ingress Controller has created a forced migration path for the many teams that relied on it as the industry standard. While the Ingress API is not yet officially deprecated, the Kubernetes SIG Network has designated the Gateway API as its official successor. Legacy Ingress will no longer receive enhancements and exists primarily for backward compatibility.

Why the Industry is Standardizing on Gateway API

While the Ingress API served the community for years, it reached a functional ceiling. Calico Ingress Gateway implements the Gateway API to provide:

  • Role-Oriented Design: Clear separation between the infrastructure (managed by SREs) and routing logic (managed by Developers).
  • Native Expressiveness: Features like URL rewrites and header manipulation Continue reading

With GenAI Turbochargers, Google Is Shifting Its Cloud Into A Higher Gear

Here is how we know computing could eventually be a peer to energy, transportation, sustenance, and healthcare as a basic infrastructure need – and will be a bigger part of our lives in the future, if the hyperscalers and cloud builders have their way: The front loading of enormous capital expenses. …

With GenAI Turbochargers, Google Is Shifting Its Cloud Into A Higher Gear was written by Timothy Prickett Morgan at The Next Platform.

N4N048: QoS Fundamentals

Quality of Service (QoS) is a huge topic with a punishingly large group of acronyms. Join Ethan and Holly as they help you build a mental framework of what QoS is and what it solves. Not only do they break down essential acronyms, they also discuss QoS fundamentals, define the major groups of QoS tools,... Read more »
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