Blog Posts in September 2014

Replacing a Central Firewall

During one of my ExpertExpress engagements I got an interesting question: “could we replace a pair of central firewalls with iptables on the Linux server?

Short answer: Maybe (depending on your security policy), but I’d still love to see some baseline scrubbing before the traffic hits the server – after all, if someone pwns your server, he’ll quickly turn off iptables.

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Quick Guide to my Interop New York Sessions

I’m running or participating in five workshops or sessions during next week’s Interop New York. Three of them build on each other, so you might want to attend all of them in sequence:

Designing Infrastructure for Private Clouds starts with requirements gathering phase and focuses on physical infrastructure design decisions covering compute, storage, physical and virtual networking, and network services. If you plan to build a private (or a reasonable small public) cloud, start here.

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Network Programmability 101: The Problem

In the first part of the Network Programmability webinar Matt Oswalt described some of the major challenges most networks are facing today:

  • Why is everyone claiming that the network is so slow to change?
  • Is that really the case? Why?
  • Why is the manual configuration culture so widespread in networking?
  • How does the holistic thinking in the design phase dissolve into the box mentality of CLI commands?
  • How does the box mentality limit the scalability of network deployments?
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Connecting Virtual Routers to the Outside World

Stefan de Kooter (@sdktr) sent me a follow-up question to my Going All Virtual with Virtual WAN Edge Routers blog post:

How would one interface with external Internet in this scenario? I totally get the virtual network assets mantra, but even a virtual BGP router would need to get a physical interconnect one way or another.

As always, there are plenty of solutions depending on your security needs.

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Formal Announcement: Software Gone Wild Podcast

If you’ve been reading my blog in the last few months, you might have noticed that I started a new podcast focused on software-defined everything (hence the name: Software Gone Wild – thanks to Jason Edelman).

The latest episodes are always available on this page; you can also subscribe to the podcast feed in RSS, Atom or iTunes format… and if you wonder why we need yet-another podcast, read the About Software Gone Wild document.

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Virtual Networking in CloudStack

If you mention open-source cloud orchestration tools these days, everyone immediately thinks about OpenStack (including the people who spent months or years trying to make it ready for production use). In the meantime, there are at least two other comparable open-source products (CloudStack and Eucalyptus) that nobody talks about. Obviously having a working product is not as sexy as having 50+ vendors and analysts producing press releases.

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Dynamic FCoE – Sparse-Mode FCoE Strikes Again

A while ago Cisco added dynamic FCoE support to Nexus 5000 switches. It sounded interesting and I wanted to talk about it in my Data Center Fabrics update session, but I couldn’t find any documentation at that time.

In the meantime, the Configuring Dynamic FCoE Using FabricPath configuration guide appeared on Cisco’s web site and J Metz wrote a lengthly blog post explaining how it all works, triggering a severe attack of déjà vu.

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The Four Paths to SDN

After the initial onslaught of SDN washing, four distinct approaches to SDN have started to emerge, from centralized control plane architectures to smart reuse of existing protocols.

As always, each approach has its benefits and drawbacks, and there’s no universally best solution. You just got four more (somewhat immature) tools in your toolbox. And now for the details.

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SIGS & Carrier’s Lunch DC Day: An Event Definitely worth Visiting

I spent last Tuesday in Bern attending the SIGS DC Day Event, and came back home extremely pleasantly surprised. The conference was nice and cozy, giving everyone plenty of opportunities to chat about data center technical challenges (thanks for all the wonderful conversations we had – you know who you are!).

Having the opportunity to meet fellow networking engineers and compare notes is great, but it’s even better to combine that with new knowledge, and that’s where the event really excelled.

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Open-Source Hybrid Cloud Reference Architecture on Software Gone Wild

A while ago Rick Parker told me about his amazing project: he started a meetup group that will build a reference private/hybrid cloud heavily relying on virtualized network services, and publish all documentation related to their effort, from high-level architecture to device and software configurations, and wiring plans.

In Episode 8 of Software Gone Wild Rick told us more about his project, and we simply couldn’t avoid a long list of topics including:

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IPv6 Neighbor Discovery (ND) and Multicast Listener Discovery (MLD) Challenges

A few days ago Garrett Wollman published his exasperating experience running IPv6 on large L2 subnets with Juniper Ex4200 switches, concluding that “… much in IPv6 design and implementation has been botched by protocol designers and vendors …” (some of us would forcefully agree) making IPv6 “…simply unsafe to run on a production network…

The resulting debate on Hacker News is quite interesting (and Andrew Yourtchenko is trying hard to keep it close to facts) and definitely worth reading… but is ND/MLD really as broken as some people claim it is?

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Is Anyone Using DMVPN-over-IPv6?

One of my readers sent me an interesting challenge: they’re deploying a new DMVPN WAN, and as they cannot expect all locations to have native (non-NAT) IPv4 access, they plan to build the new DMVPN over IPv6. He was wondering whether it would work.

Apart from “you’re definitely going in the right direction” all I could tell him was “looking at the documentation I couldn’t see why it wouldn’t work” Has anyone deployed DMVPN over IPv6 in a production network? Any hiccups? Please share your experience in the comments. Thank you!

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Snabb Switch Deep Dive on Software Gone Wild

The pilot episode of Software Gone Wild podcast featuring Snabb Switch created plenty of additional queries (and thousands of downloads) – it was obviously time for another deep dive episode discussing the intricate innards of this interesting virtual switch.

During the deep dive Luke Gorrie, the mastermind behind the Snabb Switch, answered a long list of questions, including:

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Just Published: SDN and OpenFlow – The Hype and the Harsh Reality

If you’re a regular reader of my blog, you know that I spent a lot of time during the last three years debunking SDN myths, explaining the limitations of OpenFlow and pointing out other technologies one could use to program the network.

During the summer of 2014 I organized my SDN- and OpenFlow-related blog posts into a digital book. I want to make this information as useful and as widely distributed as possible – for a limited time you can download the PDF free of charge.

Learn more about the book

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Network Infrastructure as Database

A while ago I wrote about the idea of treating network infrastructure (and all other infrastructure) as code, and using the same processes application developers are using to write, test and deploy code to design and implement networks.

That approach clearly works well if you can virtualize (and clone ad infinitum) everything. We can virtualize appliances or even routers, but installed equipment and high-speed physical infrastructure remain somewhat resistant to that idea. We need a different paradigm, and the best analogy I could come up with is a database.

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