Ivan Pepelnjak

Author Archives: Ivan Pepelnjak

Automation Win: Configure Cisco ACI with an Ansible Playbook

This blog post was initially sent to subscribers of my mailing list. Subscribe here.

Following on his previous work with Cisco ACI Dirk Feldhaus decided to create an Ansible playbook that would create and configure a new tenant and provision a vSRX firewall for the tenant when working on the Create Network Services hands-on exercise in the Building Network Automation Solutions online course.

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New: Expert ipSpace.net Subscription

Earlier this month I got this email from someone who had attended one of my online courses before and wanted to watch another one of them:

Is it possible for you to bundle a 1 year subscription at no extra cost if I purchase the Building Next-Generation Data Center course?

We were planning to do something along these lines for a long time, and his email was just what I needed to start a weekend-long hackathon.

End result: Expert ipSpace.net Subscription. It includes:

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Leaf-and-Spine Fabric Myths (Part 3)

Evil CCIE concluded his long list of leaf-and-spine fabric myths (more in part 1 and part 2) with a layer-2 fabric myth:

Layer 2 Fabrics can't be extended beyond 2 Spine switches. I had a long argument with a $vendor guys on this. They don't even count SPB as Layer 2 fabric and so forth.

The root cause of this myth is the lack of understanding of what layer-2, layer-3, bridging and routing means. You might want to revisit a few of my very old blog posts before moving on: part 1, part 2, what is switching, layer-3 switches and routers.

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MUST READ: Operational Security Considerations for IPv6 Networks

A team of IPv6 security experts I highly respect (including my good friends Enno Rey, Eric Vyncke and Merike Kaeo) put together a lengthy document describing security considerations for IPv6 networks. The document is a 35-page overview of things you should know about IPv6 security, listing over a hundred relevant RFCs and other references.

No wonder enterprise IPv6 adoption is so slow – we managed to make a total mess.

Event-Driven Network Automation in Network Automation Online Course

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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Why Is Network Automation such a Hot Topic?

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

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.

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Worth Watching: Machine Learning in a Nutshell

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.

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Feedback: Ansible for Networking Engineers

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:

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VXLAN and EVPN on Hypervisor Hosts

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.

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Leaf-and-Spine Fabric Myths (Part 1)

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.

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Network Automation Development Environments

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:

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

Network Troubleshooting Guidelines

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!

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Don’t Make a Total Mess When Dealing with Exceptions

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).

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Implications of Valley-Free Routing in Data Center Fabrics

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.

For example, when the link between L1 and C1 in the following diagram fails, there’s no connectivity between L1 and C1 as there’s no valley-free path between them.

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Infrastructure-as-Code Tools

This is the fourth blog post in “thinking out loud while preparing Network Infrastructure as Code presentation for the network automation course” series. Previous posts: Network-Infrastructure-as-Code Is Nothing New, Adjusting System State and NETCONF versus REST API.

Dmitri Kalintsev sent me a nice description on how some popular Infrastructure-as-Code (IaC) tools solve the challenges I described in The CRUD Hell section of Infrastructure-as-Code, NETCONF and REST API blog post:

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Upcoming Webinars and Events: October 2018

The fast pace of webinars continues in October 2018:

There are no on-site events planned until early December:

You can attend all upcoming webinars with an ipSpace.net webinar subscription. Online courses and on-site events require separate registration.

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