SDN For Dummies – Part Zwei

So Jacob and all the router geeks are still shaking their heads from Part Eins “Who needs routing”. “You’ll have to pry my Nexus 7000 out of my cold dead hands” they say. In fact routing is becoming more important they point out as we have to tunnel L2 virtual world traffic over L3 (to make a subnet look geographically neutral) and for VLAN separation.  (hold on to these thoughts, old school)

Before we dive into SDN, let’s review what the server side of the equation looks like and start defining some terms.

Back in 1991, this Dreez dinosaur use to play a Macintosh game called SpaceHO! I only had a Sun Workstation at the time, so to get this game running we had to use a Macintosh emulator software package. Space Ho was a multi player game so it was able to network to other players. To get to the network there was a virtual network cable that attached to the host’s physical network cable and used the host’s real IP address. This virtual network cable was Version 1 of SDN. And this Macintosh emulator was the forerunner of The Cloud…but it only hosted 1 virtual guest…a Macintosh environment.


Everyone is probably familiar with VMworkstation (damn I should of bought stock in them). The Mac Emulator above had babies and now can run multiple guests in a virtual world and they could all network with each other over virtual switches – all inside a single computer.


Enter today’s Vsphere. Now you can have multiple physical hosts and the virtual guests can run on any of them and you don’t even know where the virtual guest is running at any giving moment. Virtual guests can even move between physical hosts (vMotion).

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Dreez’s Cloud Definition: The ability of a virtual guest to execute on any piece of physical hardware without the application nor the end user knowing where it is executing.

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So in the diagram below The Cloud is Vmware’s Vsphere…the total package that makes virtual guests execute and float throughout The Cloud. A portion of Vsphere is NSX…the underlying SDN software that makes it all transparent to the physical world……


Enter Vmware’s version of SDN…NSX….

In this virtual world VMware’s NSX is distributed across each VMware Hypervisor running on each physical platform…but it runs as though it is a single piece of software.  NSX is the NETWORKING portion that supports The Cloud. NSX knows how to emulate switches/routers/routing protocols/spanning tree/etc/support/etc….all in software. But most importantly…. when a guest moves between physical hosts NSX makes sure that the IP address, security context, peer communications, VPN, etc will never change – The Operational Context – Vmotion. NSX keeps track of all this inside NSX and when the guest moves, NSX keeps contextual info floating with it.

Think of Google. Thousands of Linux PCs out there and you never know or care which one you are executing on…and it may change moment to moment. All possible with their version of SDN.

Next up SDN…….

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Helen's Loom

"Peculiar travel suggestions are dancing lessons from God." - Kurt Vonnegut

Life Stories from Dreez

These are stories from my travels. Generally I like to write stories about local people that I meet and also brag about living the retirement dream with my #1 wife Gaby. She is also my only wife.

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