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Building network automation solutions

9 module online course

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Do You Really Want to Write that Book?

It’s amazing how interesting questions come in batches: within 24 hours two friends asked me what I think about writing books. Here’s a summary of my replies (as always, full of opinions and heavily biased), and if you’re a fellow book author with strong opinions, please leave them in the comments.

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Sad News: I’m Not Coming to Interop Las Vegas

Long story short: I burned out last autumn and still haven’t recovered.

I managed to find a replacement instructor for three of my workshops, so I hope they’ll still take place. I’m also working on other ways of delivering them to whoever is interested in an interactive live session.

To all the people who wanted to meet me in Las Vegas: I’m really sorry I’ll miss you. Interop was always a great place for interesting conversations and awesome workshop audiences.

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SDN and Whitebox Switches

Some people conflate SDN with whitebox switches preferably running Linux. So what exactly is software-hardware disaggregation, and how do whitebox switches and third-party network operating systems fit into the bigger picture?

I tried to answer these questions in the SDN is not whitebox switching part of (free) Introduction to SDN webinar.

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Sysadmins Shouldn’t Be Involved with Routing

I had a great chat with Enno Rey the morning before Troopers 2016 started in which he he made an interesting remark:

I disagree with your idea of running BGP on servers because I think sysadmins shouldn’t be involved with routing.

As (almost) always, it turned out that we were still in violent agreement ;)

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How Hard Is It to Think about Failures?

Mr. A. Anonymous, frequent contributor to my blog posts left this bit of wisdom comment on the VMware NSX Update blog post:

I don't understand the statement that "whole NSX domain remains a single failure domain" because the 3 NSX controllers are deployed in the site with primary NSX manager.

I admit I was a bit imprecise (wasn’t the first time), but is it really that hard to ask oneself “what happens if the DCI link fails?

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x86-Based Switching at Ludicrous Speed on Software Gone Wild

Imagine you want to have an IPv6-only access network and transport residual IPv4 traffic tunneled across it. Sounds great, but you need to terminate those tunnels and encapsulate/decapsulate IPv4 traffic at multi-gigabit rate.

There are plenty of reassuringly-expensive hardware solutions that can do that, or you could work with really smart people and get software-based solution that can do 20 Gbps per CPU core.

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Table Sizes in OpenFlow Switches

This article was initially sent to my SDN mailing list. To register for SDN tips, updates, and special offers, click here.

Usman asked a few questions in his comment on my blog, including:

At the moment, local RIB gets downloaded to FIB and we get packet forwarding on a router. If we start evaluating too many fields (PBR) and (assume) are able to push these policies to the FIB - what would become of the FIB table size?

Short answer: It would explode ;)

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Don’t Run OSPF with Your Customers

Salman left an interesting comment on my Running BGP on Servers blog post:

My prior counterparts thought running OSPF on Mainframes was a good idea. Then we had a routing blackhole due to misconfiguration on the server. Twice! The main issue was the Mainframe admins lack of networking/OSPF knowledge.

Well, there’s a reason OSPF is called Interior Routing Protocol.

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Featured Webinar: Leaf-and-Spine Designs

The featured webinar in March 2016 is the Leaf-and-Spine Designs update to the Leaf-and-Spine Fabrics webinar, and in the featured videos (the ones marked with a star) you'll find in-depth explanation of BGP features available in Cumulus Linux, including a cool trick that allows you to run EBGP sessions across unnumbered interfaces.

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How Realistic Is High-Density Virtualization?

A while ago I guestimated that most private clouds don’t have more than a few thousand VMs, and that they don’t need more bandwidth than what two ToR switches could provide.

Last autumn Iwan Rahabok published a blog post describing the compute- and storage parts of it, and I had a presentation describing the networking aspects of high-density consolidation. However…

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Data Center Fabrics and SDN

A few days ago Inside-IT published an interview Christoph Jaggi did with me. In case you don’t understand German, here’s the English version of it.

There is a lot of talk about data center fabrics. What problem do they try to solve?

The data center fabrics are supposed to solve a simple-to-define problem: building a unified data center infrastructure that seamlessly supports data and storage communications. As always, the devil hides in the details.

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You Want Your Network to Be like Google’s? Really?

This article was initially sent to my SDN mailing list. To register for SDN tips, updates, and special offers, click here.

During one of my SDN workshops one of the attendees working for a mid-sized European ISP asked me this question:

Our management tells us we should build our network like Google does, including building our own switches. Where should we start?

The only answer I could give him was “You don’t have a chance.

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Spanning Tree Protocol (STP) and Bridging Loops

Continuing our bridging loops discussion Christoph Jaggi sent me another question:

Theoretically STP should avoid bridging loops, and yet you claim they cause data center meltdowns. What am I missing?

In theory, STP avoids bridging loops. In practice, there are numerous reasons STP got a bad name.

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