Using Unequal-Cost Multipath to Cope with Leaf-and-Spine Fabric Failures

Scott submitted an interesting the comment to my Does Unequal-Cost Multipath (UCMP) Make Sense blog post:

How about even Large CLOS networks with the same interface capacity, but accounting for things to fail; fabric cards, links or nodes in disaggregated units. You can either UCMP or drain large parts of your network to get the most out of ECMP.

Before I managed to write a reply (sometimes it takes months while an idea is simmering somewhere in my subconscious) Jeff Tantsura pointed me to an excellent article by Erico Vanini that describes the types of asymmetries you might encounter in a leaf-and-spine fabric: an ideal starting point for this discussion.

Starting Network Automation for Non-Programmers

The reader asking about infrastructure-as-code in public cloud deployments also wondered whether he has any chance at mastering on-premises network automation due to lack of programming skills.

I am starting to get concerned about not knowing automation, IaC, or any programming language. I didn’t go to college, like a lot of my peers did, and they have some background in programming.

First of all, thanks a million to everyone needs to become a programmer hipsters for thoroughly confusing people. Now for a tiny bit of reality.

Starting Network Automation for Non-Programmers

The reader asking about infrastructure-as-code in public cloud deployments also wondered whether he has any chance at mastering on-premises network automation due to lack of programming skills.

I am starting to get concerned about not knowing automation, IaC, or any programming language. I didn’t go to college, like a lot of my peers did, and they have some background in programming.

First of all, thanks a million to everyone needs to become a programmer hipsters for thoroughly confusing people. Now for a tiny bit of reality.

Worth Reading: Get Better at Programming by Learning How Things Work

Who would have thought that you could get better at what you do by figuring out how things you use really work. I probably made that argument (about networking fundamentals) too many times; Julia Evans claims the same approach applies to programming.

Worth Reading: Get Better at Programming by Learning How Things Work

Who would have thought that you could get better at what you do by figuring out how things you use really work. I probably made that argument (about networking fundamentals) too many times; Julia Evans claims the same approach applies to programming.

MUST READ: Machine Learning is a Marvelously Executed Scam

I thought I was snarky and somewhat rude (and toned down some of my blog posts on second thought), but I’m a total amateur compared to Corey Quinn. His last masterpiece – Machine Learning is a Marvelously Executed Scam – is another MUST READ.

MUST READ: Machine Learning is a Marvelously Executed Scam

I thought I was snarky and somewhat rude (and toned down some of my blog posts on second thought), but I’m a total amateur compared to Corey Quinn. His last masterpiece – Machine Learning is a Marvelously Executed Scam – is another MUST READ.

Video: Transparent Bridging Fundamentals

Years ago I wrote a series of blog posts comparing transparent bridging and IP routing, and creating How Networks Really Work materials seemed like a perfect opportunity to make that information more structured, starting with Transparent Bridging Fundamentals.

Video: Transparent Bridging Fundamentals

Years ago I wrote a series of blog posts comparing transparent bridging and IP routing, and creating How Networks Really Work materials seemed like a perfect opportunity to make that information more structured, starting with Transparent Bridging Fundamentals.

Fundamentals: Is Switching Latency Relevant?

One of my readers wondered whether it makes sense to buy low-latency switches from Cisco or Juniper instead of switches based on merchant silicon like Trident-3 or Jericho (regardless of whether they are running NX-OS, Junos, EOS, or Linux).

As always, the answer is it depends, but before getting into the details, let’s revisit what latency really is. We’ll start with a simple two-node network.

Fundamentals: Is Switching Latency Relevant?

One of my readers wondered whether it makes sense to buy low-latency switches from Cisco or Juniper instead of switches based on merchant silicon like Trident-3 or Jericho (regardless of whether they are running NX-OS, Junos, EOS, or Linux).

As always, the answer is it depends, but before getting into the details, let’s revisit what latency really is. We’ll start with a simple two-node network.

Netsim-tools Release 0.5 Work with Containerlab

TL&DR: If you happen to like working with containers, you could use netsim-tools release 0.5 to provision your container-based Arista EOS labs.

Why does it matter? Lab setup is blindingly fast, and it’s easier to integrate your network devices with other containers, not to mention the crazy idea of running your network automation CI pipeline on Gitlab CPU cycles. Also, you could use the same netsim-tools topology file and provisioning scripts to set up container-based or VM-based lab.

What is containerlab? A cool project that builds realistic virtual network topologies with containers. More details…

Netsim-tools Release 0.5 Work with Containerlab

TL&DR: If you happen to like working with containers, you could use netsim-tools release 0.5 to provision your container-based Arista EOS labs.

Why does it matter? Lab setup is blindingly fast, and it’s easier to integrate your network devices with other containers, not to mention the crazy idea of running your network automation CI pipeline on Gitlab CPU cycles. Also, you could use the same netsim-tools topology file and provisioning scripts to set up container-based or VM-based lab.

What is containerlab? A cool project that builds realistic virtual network topologies with containers. More details…

Must Read: Automate Nexus-OS Fabric Deployment

Some networking engineers breeze through our Network Automation online course, others disappear after a while… and a few of those come back years later with a spectacular production-grade solution.

Stephen Harding is one of those. He attended the automation course in spring 2019 and I haven’t heard from him in almost two years… until he submitted one of the most mature data center fabric automation solutions I’ve seen.

Not only that, he documented the solution in a long series of must-read blog posts. Hope you’ll find them useful; I liked them so much I immediately saved them to Internet Archive (just in case).

Must Read: Automate Nexus-OS Fabric Deployment

Some networking engineers breeze through our Network Automation online course, others disappear after a while… and a few of those come back years later with a spectacular production-grade solution.

Stephen Harding is one of those. He attended the automation course in spring 2019 and I haven’t heard from him in almost two years… until he submitted one of the most mature data center fabric automation solutions I’ve seen.

Not only that, he documented the solution in a long series of must-read blog posts. Hope you’ll find them useful; I liked them so much I immediately saved them to Internet Archive (just in case).

Start Automating Public Cloud Deployments with Infrastructure-as-Code

One of my readers sent me a series of “how do I get started with…” questions including:

I’ve been doing networking and security for 5 years, and now I am responsible for our cloud infrastructure. Anything to do with networking and security in the cloud is my responsibility along with another team member. It is all good experience but I am starting to get concerned about not knowing automation, IaC, or any programming language.

No need to worry about that, what you need (to start with) is extremely simple and easy-to-master. Infrastructure-as-Code is a simple concept: infrastructure configuration is defined in machine-readable format (mostly text files these days) and used by a remediation tool like Terraform that compares the actual state of the deployed infrastructure with the desired state as defined in the configuration files, and makes changes to the actual state to bring it in line with how it should look like.

Start Automating Public Cloud Deployments with Infrastructure-as-Code

One of my readers sent me a series of “how do I get started with…” questions including:

I’ve been doing networking and security for 5 years, and now I am responsible for our cloud infrastructure. Anything to do with networking and security in the cloud is my responsibility along with another team member. It is all good experience but I am starting to get concerned about not knowing automation, IaC, or any programming language.

No need to worry about that, what you need (to start with) is extremely simple and easy-to-master. Infrastructure-as-Code is a simple concept: infrastructure configuration is defined in machine-readable format (mostly text files these days) and used by a remediation tool like Terraform that compares the actual state of the deployed infrastructure with the desired state as defined in the configuration files, and makes changes to the actual state to bring it in line with how it should look like.

Worth Reading: Fail-Fast is Failing… Fast

Here’s an interesting fact: cloud-based stuff often refuses to die; it might become insufferably slow, but would still respond to the health checks. The usual fast failover approach used in traditional high-availability clusters is thus of little use.

For more details, read the ‌Fail-Fast is Failing… Fast ACM Queue article.

Worth Reading: Fail-Fast is Failing… Fast

Here’s an interesting fact: cloud-based stuff often refuses to die; it might become insufferably slow, but would still respond to the health checks. The usual fast failover approach used in traditional high-availability clusters is thus of little use.

For more details, read the ‌Fail-Fast is Failing… Fast ACM Queue article.

Worth Reading: Data Manipulation in Jinja2

Ansible and Jinja2 are not an ideal platform for data manipulation, but sometimes it’s easier to hack together something in Jinja2 than writing a Python filter. In those cases, you might find the Data Model Transformation with Jinja2 by Philippe Jounin extremely useful.