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Quantum Computing and OpenFlow

I read an excellent rant by prof. Victor Galitski describing the current explosion of Quantum Computing hype, and couldn’t help being reminded of the OpenFlow brouhaha we experienced almost a decade ago – you could do a simple search-and-replace and the article would have been equally valid.

Enjoy… and remember the details for the next time your beloved vendor comes along with Quantum Computing slide deck.

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Designing Networks: From Tricycles to Aircraft Carriers

I planned to take my summer break seriously and stop blogging until late August, but then I shouldn’t have looked at my Twitter feed (my bad), where the AI algorithms selected just the right morsel to trigger the maximum rantiness. I would strongly recommend you read the original tweet and all the responses first – it looks like it was a serious suggestion, not a trolling exercise.

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Thank You for Everything Irena, We'll Miss You Badly

In February 2018, Irena Marčetič joined to fix the (lack of) marketing. After getting that done, she quickly took over most of sales, support, logistics, content production, guest speaker coordination… If you needed anything from us in the last few years, it was probably Irena answering your requests and helping you out.

She did a fantastic job and transformed from Ivan and an occasional guest speaker to a finely tuned machine producing several hours of new content every month. She organized our courses, worked with guest speakers, podcast guests and hosts, participated in every guest speaker webinar to take notes for the editing process, managed content editing, watched every single video we created before it was published to make sure the audio was of acceptable quality and all the bloopers were removed… while answering crazy emails like I need you to fill in this Excel spreadsheet with your company data because I cannot copy-paste that information from your web site myself and solving whatever challenges our customers faced.

Unfortunately, Irena decided to go back to pure marketing and is leaving today. Thanks a million for all the great work – we’ll badly miss you.

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Webinars in the First Half of 2021

It’s time for another this is what we did in the last six months blog post. Instead of writing another wall-of-text, I just updated the one I published in early January. Here are the highlights:

That’s about it for the first half of 2021. I’ll be back in early September.

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Video: Typical Large-Scale Bridging Use Cases

In the previous video in the Switching, Routing and Bridging section of How Networks Really Work webinar we compared transparent bridging with IP routing. Not surprisingly (given my well-known bias toward stable solutions) I recommended using IP routing as much as possible, but there are still people out there pushing large-scale transparent bridging solutions.

In today’s video we’ll look at some of the supposed use cases and stable solutions you could use instead of stretching a virtual thick yellow cable halfway across a continent.

The video is available with Free Subscription.
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Stretched VLANs: What Problem Are You Trying to Solve?

One of subscribers sent me this interesting question:

I am the network administrator of a small data center network that spans 2 buildings. The main building has a pair of L2/L3 10G core switches. The second building has a stack of access switches connected to the main building with 10G uplinks. This secondary datacenter has got some ESX hosts and NAS for remote backup and some VM for development and testing, but all the Internet connection, firewall and server are in the main building.

There is no routing in the secondary building and most of the VLANs are stretched. Do you think I must change that (bringing routing to the secondary datacenter), or keep it simple like it is now?

As always, it depends, this time on what problem are you trying to solve?

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Why Do We Need BGP-LS?

One of my readers sent me this interesting question:

I understand that an SDN controller needs network topology information to build traffic engineering paths with PCE/PCEP… but why would we use BGP-LS to extract the network topology information? Why can’t we run OSPF with controller by simulating a software based OSPF instance in every area to get topology view?

There are several reasons to use BGP-LS:

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Unexpected Interactions Between OSPF and BGP

It started with an interesting question tweeted by @pilgrimdave81

I’ve seen on Cisco NX-OS that it’s preferring a (ospf->bgp) locally redistributed route over a learned EBGP route, until/unless you clear the route, then it correctly prefers the learned BGP one. Seems to be just ooo but don’t remember this being an issue?

Ignoring the “why would you get the same route over OSPF and EBGP, and why would you redistribute an alternate copy of a route you’re getting over EBGP into BGP” aspect, Peter Palúch wrote a detailed explanation of what’s going on and allowed me to copy into a blog post to make it more permanent:

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Comparing EVPN with Flood-and-Learn Fabrics

One of subscribers sent me this question after watching the EVPN Technical Deep Dive webinar:

Do you have a writeup that compares and contrasts the hardware resource utilization when one uses flood-and-learn or BGP EVPN in a leaf-and-spine network?

I don’t… so let’s fix that omission. In this blog post we’ll focus on pure layer-2 forwarding (aka bridging), a follow-up blog post will describe the implications of adding EVPN IP functionality.

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Questions about BGP in the Data Center (with a Whiff of SRv6)

Henk Smit left numerous questions in a comment referring to the Rethinking BGP in the Data Center presentation by Russ White:

In Russ White’s presentation, he listed a few requirements to compare BGP, IS-IS and OSPF. Prefix distribution, filtering, TE, tagging, vendor-support, autoconfig and topology visibility. The one thing I was missing was: scalability.

I noticed the same thing. We kept hearing how BGP scales better than link-state protocols (no doubt about that) and how you couldn’t possibly build a large data center fabric with a link-state protocol… and yet this aspect wasn’t even mentioned.

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