Event-driven automation (changing network state and/or configuration based on events) is the holy grail of network automation. Imagine being able to change routing policies (or QoS settings, or security rules) based on changes in the network.

We were able to automate simple responses with on-box solutions like Embedded Event Manager (EEM) available on Cisco IOS for years; modern network automation tools allow you to build robust solutions that identify significant events from the noise generated by syslog messages, SNMP traps and recently streaming telemetry, and trigger centralized responses that can change the behavior of the whole network.

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One of my readers asked a very valid question when reading the Why Is Network Automation So Hard blog post:

Why was network automation 'invented' now? I have been working in the system development engineering for 13+ years and we have always used automation because we wanted to save time & effort for repeatable tasks.

He’s absolutely right. We had fully-automated ISP service in early 1990’s, and numerous service providers used network automation for decades.

Found an awesome blog post describing how we’re wasting resources on incomprehensible scale. Here’s a tiny little morsel:

Only in software, it’s fine if a program runs at 1% or even 0.01% of the possible performance. Everybody just seems to be ok with it. People are often even proud about how much inefficient it is, as in “why should we worry, computers are fast enough”.

In mid-September I was invited to present at the vNIC 2018 event in Frankfurt, Germany. Unfortunately I wasn’t able to get there, but Zoom did a great job … and enabled me to record the talk.

This blog post was initially sent to the subscribers of my SDN and Network Automation mailing list. Subscribe here.

What could be better than an SDN product to bring you closer to a networking nirvana? You guessed it – an SDN product using machine learning.

Want to have some fun? The next time your beloved $vendor rep drops by trying to boost his bonus by persuading you to buy the next-generation machine-learning tool his company just released, invite him to watch James Mickens’ Usenix Security Symposium keynote with you.

The next set of Leaf-and-Spine Fabric Myths listed by Evil CCIE focused on BGP:

BGP is the best choice for leaf-and-spine fabrics.

I wrote about this particular one here. If you’re not a BGP guru don’t overcomplicate your network. OSPF, IS-IS, and EIGRP are good enough for most environments. Also, don’t ever turn BGP into RIP with AS-path length serving as hop count.

One of my subscribers sent me a nice email describing his struggles to master Ansible:

Some time ago I started to hear about Ansible as the new power tool for network engineer, my first reaction was “What the hell is this?” I searched the web and found many blah blahs about it… until I landed on your pages.

He found Ansible for Networking Engineers material sufficient to start an automation project:

One of my readers sent me a series of questions regarding a new cloud deployment where the cloud implementers want to run VXLAN and EVPN on the hypervisor hosts:

I am currently working on a leaf-and-spine VXLAN+ EVPN PoC. At the same time, the systems team in my company is working on building a Cloudstack platform and are insisting on using VXLAN on the compute node even to the point of using BGP for inter-VXLAN traffic on the nodes.

Using VXLAN (or GRE) encap/decap on the hypervisor hosts is nothing new. That’s how NSX and many OpenStack implementations work.

Ethan Banks wrote an awesome blog post on the characteristics of fragile engineers (most of them probably being expert beginners). I can’t help but ponder how often I behave like one…

Apart from the “they have no clue what they’re talking about” observation, Evil CCIE left a long list of leaf-and-spine fabric myths he encountered in the wild in a comment on one of my blog posts. He started with:

Clos fabric (aka Leaf And Spine fabric) is a non-blocking fabric

That was obviously true in the days when Mr. Clos designed the voice switching solution that still bears his name. In the original Clos network every voice call would get a dedicated path across the fabric, and the number of voice calls supported by the fabric equaled the number of alternate end-to-end paths.

Building the network automation lab environment seems to be one of the early showstoppers on everyone’s network automation journey. These resources might help you get started:

• I wrote an installation script that installs the myriad dependencies needed by Ansible and NAPALM in just the right order on a Ubuntu VM (step-by-step instructions for ipSpace.net subscribers).
• Carl Buchmann open-sourced a full-blown infrastructure-as-code development environment he uses for his automation projects.
• Jaap de Vos described how he creates a Docker image containing Ansible, NAPALM and Nornir.

Hint: after setting up your environment, you might want to enroll into the Spring 2019 network automation course ;)

It all started with an interesting weird MLAG bugs discussion during our last Building Next-Generation Data Center online course. The discussion almost devolved into “when in doubt reload” yammering when Mark Horsfield stepped in saying “while that may be true, make sure to check and collect these things before reloading”.

I loved what he wrote so much that I asked him to turn it into a blog post… and he made it even better by expanding it into generic network troubleshooting guidelines. Enjoy!

A while ago I had the dubious “privilege” of observing how my “beloved” airline Adria Airways deals with exceptions. A third-party incoming flight was 2.5 hours late and in their infinite wisdom (most probably to avoid financial impact) they decided to delay a half-dozen outgoing flights for 20-30 minutes while waiting for the transfer passengers.

Not surprisingly, when that weird thingy landed and they started boarding the outgoing flights (now all at the same time), the result was a total mess with busses blocking each other (this same airline loves to avoid jet bridges).

Did you know that many networking engineers use ipSpace.net webinars (and subscription) to prepare for the job interviews?

Here’s one of their success stories (name changed for obvious reasons):

As I explained in a previous blog post, most leaf-and-spine best-practices (as in: what to do if you have no clue) use BGP as the IGP routing protocol (regardless of whether it’s needed) with the same AS number shared across all spine switches to implement valley-free routing.

This design has an interesting consequence: when a link between a leaf and a spine switch fails, they can no longer communicate.