Pragmatic Data Center Fabrics

I always love to read the practical advice by Andrew Lerner. Here’s another gem that matches what Brad Hedlund, Dinesh Dutt and myself (plus numerous others) have been saying for ages:

One specific recommendation we make in the research is to “Build a rightsized physical infrastructure by using a leaf/spine design with fixed-form factor switches and 25/100G capable interfaces (that are reverse-compatible with 10G).”

There’s a slight gotcha in that advice: it trades implicit complexity of chassis switches with explicit complexity of fixed-form switches.

Interview: Programmable Infrastructure Is Just a Tool

A while ago I did an interview about programmable infrastructure that got published as an article in mid-March. As you might expect, my main message was “technology will never save you unless you change your processes to adapt to its benefits.”

Hope you’ll enjoy it!

Should I Take CCIE DC or ipSpace.net Data Center Online Course?

Got this question from a networking engineer who couldn’t decide whether to go for CCIE Data Center certification or attend my Building Next-Generation Data Center online course:

I am considering pursuing CCIE DC. I found your Next-Generation DC course very interesting. Now I am bit confused trying to decide whether to start with CCIE DC first and then do your course.

You might be in a similar position, so here’s what I told him.

ipSpace.net Subscription Now Available with PayPal

Every second blue moon someone asks me whether they could buy ipSpace.net subscription with PayPal. So far, the answer has been no.

Recently we started testing whether we could use Digital River to solve a few interesting challenges we had in the past, and as they offer PayPal as a payment option, it seemed to be a perfect fit for a low-volume trial.

The only product that you can buy with PayPal during the trial is the standard subscription – just select PayPal as the payment method during the checkout process.

Finally: the first three subscribers using PayPal will get extra 6 months of subscription.

Worth Reading: The Death of Expertise

Bruno Wollman pointed me to an excellent article on the ignorance of expertise and confidence of the dumb. Here’s the TL&DR summary (but you should really read the whole thing):

• The expert isn’t always right;
• An expert is far more likely to be right than you are;
• Experts come in many flavors – usually you need a combination of education and expertise;
• In any discussion, you have a positive obligation to learn at least enough to make the conversation possible. University of Google doesn’t count;
• While you’re entitled to have an opinion, having a strong opinion isn’t the same as knowing something.

Enjoy ;)

Video: Automatic Diagramming with PowerNSX

Here's a trick question: how often do your Visio diagrams match what's really implemented in your network?

Wouldn't it be great to be able to create or modify them on-the-fly based on what's really configured in the network? That's exactly what Anthony Burke demonstrated in the PowerNSX part of PowerShell for Networking Engineers webinar (source code).

You’ll need at least free ipSpace.net subscription to watch the video.

EVPN Route Target Considerations in EBGP Environment

The proponents of the “let’s run EVPN over EBGP underlay” idea often ignore an interesting challenge: EVPN advocates use of automatically-generated Route Targets, which might not work when every leaf switch uses a different AS number.

I explored this particular can of worms in the EVPN Route Target Considerations section of the Using BGP in a Data Center Leaf-and-Spine Fabric saga.

New in IPv6: The Next Chapter in IPv6 Multihoming Saga

Remember the IPv6 elephant in the room – the inability to do small-site multihoming without NAT (well, NPT66)? IPv6 is old enough to buy its own beer, but the elephant is still hogging the room. Tons of ideas have been thrown around in IETF (mostly based on source address selection tricks), but none of that spaghetti stuck to the wall.

Couldn’t Resist: Cheat-Proofing Certifications

Stumbled upon this paragraph on Russ White’s blog:

I don’t really know how you write a certification that does not allow someone who has memorized the feature guide to do well. How do you test for protocol theory, and still have a broad enough set of test questions that they cannot be photographed and distributed?

As Russ succinctly explained the problem is two-fold:

Container Security through Segregation

One of my readers sent me a container security question after reading the Application Container Security Guide from NIST:

We are considering segregating dev/test/prod environments with bare-metal hardware. I did not find something in the standard concerning this. What should a financial institution do in your opinion?

I am no security expert and know just enough about containers to be dangerous, but there’s a rule that usually works well: use common sense and identify similar scenarios that have already been solved.

Worth Reading: Automation: Easy Button vs Sentient Voodoo Magic Button

I’m always telling network engineers attending my network automation workshops and online courses that there’s no magic bullet or 3-steps-to- success.

You cannot automate a process until you can describe it with enough details so that someone who has absolutely no clue what should be done can execute it.

David Gee published a long (and somewhat ranty) version of that statement. Enjoy!

Video: Tools and Knobs to Use when Tweaking TCP Performance

In the second half of his Networks, Buffers and Drops webinar JR Rivers focused on end systems: what tools could you use to measure end-to-end TCP throughput, or monitor performance of an individual socket or the whole TCP stack?

You’ll need at least free ipSpace.net subscription to watch the video.

Don’t Get Obsessed with REST API

REST API is the way of the world and all network devices should support it, right? Well, Ken Duda (Arista) disagreed with this idea during his Networking Field Day presentation, but unfortunately there wasn’t enough time to go into the details that would totally derail the presentation anyway.

Fixing that omission: should we have REST API on network devices or not?

BGP in EVPN-Based Data Center Fabrics – Take 2

My BGP in EVPN-Based Data Center Fabrics blog post generated numerous comments from engineers disagreeing with my views on using IBGP-over-EBGP.

As usual, there were three kinds of comments:

New in IPv6: Stable Random IPv6 Addresses on OpenBSD

The idea of generating random IPv6 addresses (so you cannot be tracked across multiple networks based on your MAC address) that stay stable within each subnet (so you don’t pollute everyone’s ND cache every time you open your iPad) is pretty old: RFC 7217 was published almost exactly four years ago.

Linux was quick to pick it up, OpenBSD got RFC 7127 support a few weeks ago. However, there’s an Easter egg in the OpenBSD patches that implement it: SLAAC on OpenBSD now works with any prefix length (not just /64).

Data Center Routing with RIFT on Software Gone Wild

Years ago Petr Lapukhov decided that it’s a waste of time to try to make OSPF or IS-IS work in large-scale data center leaf-and-spine fabrics and figured out how to use BGP as a better IGP.

In the meantime, old-time routing gurus started designing routing protocols targeting a specific environment: highly meshed leaf-and-spine fabrics. First in the list: Routing in Fat Trees (RIFT).

VXLAN Limitations of Data Center Switches

One of my readers found this Culumus Networks article that explains why you can’t have more than a few hundred VXLAN-based VLAN segments on every port of 48-port Trident-2 data center switch.

Expect to see similar limitations in most other chipsets. There’s a huge gap between millions of segments enabled by 24-bit VXLAN Network Identifier and reality of switching silicon. Most switching hardware is also limited to 4K VLANs.

Could We Build an IXP on Top of VXLAN Infrastructure?

Andy sent me this question:

I'm currently playing around with BGP & VXLANs and wondering: is there anything preventing from building a virtual IXP with VXLAN? This would be then a large layer 2 network - but why have nobody build this to now, or why do internet exchanges do not provide this?

There was at least one IXP that was running on top of VXLAN. I wanted to do a podcast about it with people who helped them build it in early 2015 but one of them got a gag order.

Upcoming Webinars, Online Courses and Live Events

The pace of live webinar sessions will slow down a bit in April 2018 due to the onslaught of European spring holiday season. Nonetheless, you’ll be able to enjoy:

• The second part of EVPN Technical Deep Dive series with Dinesh Dutt on April 5th;
• The planning and design part of NSX, ACI or EVPN webinar with Mitja Robas on April 24th;

On April 19th we’ll have the first DIGS event in 2018, starting with introduction to SDDC and VMware NSX in the morning and NSX workshop in the afternoon.

Dunning-Kruger in IT Infrastructure

Sitting in a taxi driving to CLEUR 2018 in Barcelona we couldn’t resist but complain about the stuff we’re seeing in real-life networks, resulting in someone exclaiming something along the lines of “I can’t understand how someone could do so many stupid things”

Welcome to the wonderful world of Dunning-Kruger Effect.