Found this Douglas Adams quote in The Signal and the Noise (a must-read book):

The major difference between a thing that might go wrong and a thing that cannot possibly go wrong is that when a thing that cannot possibly go wrong goes wrong it usually turns out to be impossible to get at or repair

I’ll leave to your imagination how this relates to stretched VLANs, ACI, NSX, VSAN, SD-WAN and a few other technologies.

After explaining the challenges of data center fabric deployments, Dinesh Dutt focused on a very important topic I covered in Week#3 of the Building Network Automation Solutions online course: how do you separate data (data model describing data center fabric) from code (Ansible playbooks and device configurations)

It’s always great to see students enrolled in Building Network Automation Solutions online course using ideas from my sample playbooks to implement a wonderful solution that solves a real-life problem.

James McCutcheon did exactly that: he took my LLDP-to-Graph playbook and used it to graph VLANs stretching across multiple switches (and provided a good description of his solution).

One of my readers sent me this question:

I'm having an internal debate whether to use firewall-based VPNs or DMVPN to connect several sites if our MPLS connection goes down. How would you handle it? Do you have specific courses answering this question?

As always, the correct answer is it depends, in this case on:

Third vendor in this year’s series of data center switching updates: Cisco.

As expected, Cisco launched a number of new switches in 2017, and EOL’d older models … for pretty varying value of old. For example, most of the original Nexus 9300 models are gone.

Everyone knows that Service Providers and Enterprise networks diverged decades ago. More precisely, organizations that offer network connectivity as their core business usually (but not always) behave differently from organizations that use networking to support their core business.

Obviously, there are grey areas: from people claiming to be service providers who can’t get their act together, to departments (or whole organizations) who run enterprise networks that look a lot like traditional service provider networks because they’re effectively an internal service provider.

One of my readers coming from system development area asked a fundamental question about the role of automation in enterprise IT (somewhat paraphrased):

[In system development] we automate typical tasks from the pre-defined task repository, so I would like to understand broader context as the automation (I guess) is just a part of the change we want to do in the system. Someone needs to decide what to do, someone needs to accept the change and finally the automation is used.

Of course he’s absolutely right.

I love reading well-argued contrarian views, and Geoff Huston’s Opinion in Defense of NAT is definitely worth the time it will take you to read it.

TL&DR: Geoff argues that with all the wastage going on in IPv6 land (most bizarre: let’s give a /48 to every residential subscriber) the number of bits available for IPv6 endpoint addressing gets close to what we can squeeze out of IPv4 NAT.

One of the undergraduate students attending my Ansible for Networking Engineers online course got to the point where he wanted to start hands-on work and sent me a list of questions:

Do I have to buy a VIRL license to use your Ansible course materials? Or is VIRL in any Github repository? Is there a way to use your files in a free Tool like GNS3?

Let’s go through them one by one:

During Cisco Live Berlin 2017 Peter Jones (chair of several IEEE task forces) and myself went on a journey through 40 years of Ethernet history (and Token Bus and a few other choice technologies).

The sound quality is what you could expect from something recorded on a show floor with pigeons flying around, but I hope you’ll still enjoy our chat.