Understanding Shortest Path First

Link state protocols like OSPF and IS-IS use the Shortest Path First (SPF) algorithm developed by Edsger Dijkstra. Edsger was a Dutch computer scientist, programmer, software engineer, mathematician, and science essayist. He wanted to solve the problem of finding the shortest distance between two cities such as Rotterdam and Groningen. The solution came to him when sitting in a café and the rest is history. SPF is used in many applications, such as GPS, but also in routing protocols, which I’ll cover today.

To explain SPF, I’ll be working with the following topology:

Note that SPF only works with a weighted graph where we have positive weights. I’m using symmetrical costs, although you could have different costs in each direction. Before running SPF, we need to build our Link State Database (LSDB) and I’ll be using IS-IS in my lab for this purpose. Based on the topology above, we can build a table showing the cost between the nodes:

This triplet of information consists of originating node, neighbor node, and cost. It can also be represented as [R1, R2, 2], [R1, R3, 8], [R2, R1, 2], [R2, R3, 5], [R2, R4, 6], [R3, R1, 8], [R3, R2, 5], [R3, R4, Continue reading

NB528: IP Fabric Adds Firewall Rule Simulation; Extreme Networks Debuts Agentic AI in Platform ONE

Take a Network Break! We begin with a Red Alert for critical vulnerabilities Kubernetes Gardener. Up next, a threat actor has been squatting on unused CNAME records to distribute malware and spam, and IP Fabric rolls out a new firewall rule simulation capability to let administrators test the effect of firewall rules on traffic patterns.... Read more »

ChatGPT Strikes Again: IS-IS on Unnumbered Interfaces 🤦‍♂️

In the last few days, I decided to check out how much better ChatGPT has gotten in the last year or two. I tried to be positive and was rewarded with some surprisingly good results. I even figured out I can use it to summarize my blog posts using prompts like this one:

Using solely the information from blog.ipspace.net, what can you tell me about running ospf over unnumbered interfaces

And then I asked it about unnumbered interfaces and IS-IS, and it all went sideways:

Read more …

Why we need a unified approach to Kubernetes environments

Today, organizations struggle managing disparate technologies for their Kubernetes networking and network security needs. Leveraging multiple technologies for networking and security for in-cluster, ingress, egress, and traffic across clusters creates challenges, including operational complexities and increased costs. For example, to manage ingress traffic for Kubernetes clusters, users cobble together multiple solutions from different providers such as ingress controllers or gateways and load balancers for routing traffic, as well as Web Application Firewalls (WAFs) for enhanced security.

Despite the challenges it brings, deploying disparate technologies has been a “necessary evil” for organizations to get all the capabilities needed for holistic Kubernetes networking. Here, we’ll explore challenges this proliferation of tooling introduces, and provide actionable tips for today’s platform and security teams to overcome these issues.

Challenges Managing Multiple Technologies

The fragmented approach to networking and network security in Kubernetes leads to challenges and inefficiencies, including:

  • Operational overhead: Each technology comes with its own learning curve, setup, configuration, integration, and maintenance requirements. This leads to a challenging user experience.
  • Increased costs: Licensing and operational costs accumulate as more tools are deployed.
  • Scaling challenges: As clusters grow or spread across diverse environments, ensuring consistent and secure networking becomes harder.
  • Security gaps: Disjointed solutions Continue reading

Repost: On the Advantages of XML

Continuing the discussion started by my Breaking APIs or Data Models Is a Cardinal Sin and Screen Scraping in 2025 blog posts, Dr. Tony Przygienda left another thoughtful comment worth reposting as a publicly visible blog post:

Having read your newest rant around my rant ;-} I can attest that you hit the nail on the very head in basically all you say:

  • XML output big? yeah.
  • JSON squishy syntax? yeah.
  • SSH prioritization? You didn’t live it until you had a customer where a runaway python script generated 800+ XML netconf sessions pumping data ;-)
Read more …

What is an EVPN Type 5 Route for (EVPN/VXLAN)

For EVPN/VXLAN, Type 5 routes are used for two purposes: Internally and Externally

Internally it’s used to communicate which VTEPs have a given subnet instantiated on it.

Here’s an example of the output of the command show ip bgp route-type ip-prefix ipv4 on an Arista cEOS spine running EVPN/VXLAN.

It’s showing you that 10.1.10.0/24 (VLAN 10/VNI 10010) is only available on leaf1 and leaf2 (10.1.255.1-2) and 10.1.20.0/24 (VLAN 20/VNI 10020) is only available on leaf3 and leaf4 (10.1.255.3-4). It’s eBGP so each leaf has its own ASN (you see in the path field). The next hop shows the VTEP IP (10.1.254.1-4). I checked on the spine as the spine receives all the EVPN routes from the leafs and propagates them as a route server. The spines don’t install any of these routes, they just propagates them.

       Network                Next Hop              Metric  LocPref Weight  Path

 * >      RD: 10.1.255.1:10000 ip-prefix 10.1.10.0/24
                                 10.1.254.1            -       100     0       65101 i
 * >      RD: 10.1.255.2:10000 ip-prefix 10.1.10.0/24
                                 10.1.254.2            -       100     0       65102 i
  Continue reading

Companies Must Embrace Bespoke AI Designed for IT Workflows

Although LLMs have been readily available for the past few years, inroads into the IT sector have been minimal. We have seen successful generative AI (GenAI) model penetration into SaaS solutions and areas like help desks; however, successful GenAI integration into security software has been few and far between. Generally speaking, it is not easy to repurpose an LLM to work within a security domain. LLMs are optimized for natural language; they can’t immediately understand or process security elements such as flow packets, logs, alerts, and knowledge graphs. To build out effective genAI integration in the security sphere, it’s time to embrace bespoke, foundational AI for IT workflows. AI Model Efficiency The recent trend toward building out models more efficiently, as opposed to scaling at all costs, is a natural progression of GenAI tools in the enterprise space. Despite all the LLM hype, not every business problem requires an LLM solution. If you utilize LLMs within your infrastructure, it’s best to right-size them (distill them into smaller models that address specific business problems) while focusing on privacy, security, and explainability. By right-sizing your models, compute is kept to a minimum, which prevents costs from being passed on to your customers. Continue reading

Lenovo Breaks Even On Datacenter Hardware, Makes It Up In Services

Here is how you know you are in a tough business: No matter what you do, no matter how hard your people work and how smart they are, no matter that you are riding the wild tiger of AI growth and revenues have grown marvelously, you can’t make any money. …

Lenovo Breaks Even On Datacenter Hardware, Makes It Up In Services was written by Timothy Prickett Morgan at The Next Platform.

Cloudflare named in 2025 Gartner® Magic Quadrant™ for Security Service Edge

For the third consecutive year, Gartner has named Cloudflare in the Gartner® Magic Quadrant™ for Security Service Edge (SSE) report. This analyst evaluation helps security and network leaders make informed choices about their long-term partners in digital transformation. We are excited to share that Cloudflare is one of only nine vendors recognized in this year’s report. You can read more about our position in the report here.

What’s more exciting is that we’re just getting started. Since 2018, starting with our Zero Trust Network Access (ZTNA) service Cloudflare Access, we’ve continued to push the boundaries of how quickly we can build and deliver a mature SSE platform. In that time, we’ve released multiple products each year, delivering hundreds of features across our platform. That’s not possible without our customers. Today, tens of thousands of customers have chosen to connect and protect their people, devices, applications, networks, and data with Cloudflare. They tell us our platform is faster and easier to deploy and provides a more consistent and reliable user experience, all on a more agile architecture for longer term modernization. We’ve made a commitment to those customers to continue to deliver innovative solutions with the velocity and resilience Continue reading

Resolving a request smuggling vulnerability in Pingora

On April 11, 2025 09:20 UTC, Cloudflare was notified via its Bug Bounty Program of a request smuggling vulnerability in the Pingora OSS framework discovered by a security researcher experimenting to find exploits using Cloudflare’s Content Delivery Network (CDN) free tier which serves some cached assets via Pingora.

Customers using the free tier of Cloudflare’s CDN or users of the caching functionality provided in the open source pingora-proxy and pingora-cache crates could have been exposed.  Cloudflare’s investigation revealed no evidence that the vulnerability was being exploited, and was able to mitigate the vulnerability by April 12, 2025 06:44 UTC within 22 hours after being notified.

What was the vulnerability?

The bug bounty report detailed that an attacker could potentially exploit an HTTP/1.1 request smuggling vulnerability on Cloudflare’s CDN service. The reporter noted that via this exploit, they were able to cause visitors to Cloudflare sites to make subsequent requests to their own server and observe which URLs the visitor was originally attempting to access.

We treat any potential request smuggling or caching issue with extreme urgency.  After our security team escalated the vulnerability, we began investigating immediately, took steps to disable traffic to vulnerable components, and deployed Continue reading

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