VXLAN Concept Simplified

While VXLAN seems to be the next revolutionary and world changing network technology out there, all the marketing hypes around it makes too confusing for the rest of us. When VXLANs first came out, I have decided to learn more about it. While there was tons of materials about it online, the more I read about it the more confused I was about this new magical networking technology. I have to admit while I know my ways around networking, I am still not anything near CCIE or in another word a networking whiz. I believe many more people out there who is not in the networking field are still confused about what is VXLANs and what problems it came to solve. In this post, I am trying to over simplify VXLANs for the rest of us to understand it. You can call it VXLAN for dummies if you want. I am not going to cover VXLANs in depth, but to touch on what its and where the idea of it came from.

Let’s start by a quick definition of VXLAN. Virtual Extensible LAN (VXLAN) is a proposed encapsulation protocol for running an overlay network on existing Layer 3 infrastructure. An overlay network is a virtual network that is built on top of existing network Layer 2 and Layer 3 technologies to support elastic compute architectures. VXLAN will make it easier for network engineers to scale out a cloud computing environment while logically isolating cloud apps and tenants.

For those of us who does not have a degree in networking, I hope by now you know what VXLAN is. I thought so, that definition did not make any sense to me the first time I read it either, so don’t feel a shame about it. I am sure there plenty of us out there, who would loved a simpler definition. As VXLAN is getting widely involved into Cloud Computing its hitting the desks of many CEOs, CIOs, CTOs, Architects, Managers, & many others who have a very little time to learn about VXLAN and grasp a quick understanding of it. Such a definition and most articles out there which live to the marketing hype of VXLAN will get such audience no where and will take many of us for a ride. The funny part while most of the marketing articles out there talk about VXLANs in the context of its mainly used to stretch networks/VLANs that is not what its best for at the moment and is more futuristic looking.

To understand VXLAN, you will need to understand the story behind it. Today if you wanted to isolate a group of machines, you would normally ask the network team to create you a VLAN. While this is not problematic in smaller environment, in larger one this will take a very long time to obtain a full chain of management approvals before your network team create you a new VLAN. In the old days, this was not a big deal, though in a dynamic Cloud Computing game, the demand for isolated networks to be created on the fly is increasing. Imagine if you are using a product like VMware vCloud Director to run your testing environment. You might have few dozens of different departments in your organization who want their own isolated testing environment, while you could provisioned a separate VLAN to each of them it won’t be the most flexible/efficient solution. As the network team has to go through a long approval cycle to grant you a VLAN as they are worried to run out of all the VLANs available to them as the max theoretical number of VLANs you can have in your network is 4096 where the real implementation in many networking gears can be even much less than that. Creating a separate VLAN for each testing org might seems a big waste of VLANs as well each time you need a new one you will need to go across a long cycle of approvals.

Imagine if you wanted to deploy a multi-tier application presented by multiple VMs(vAPP) multiple times without changing computer name or IP to allow multiple developer or tester to use it & be able to communicate with other tester using the same computer name or IPs other testers use to make quicker sense of the information exchange among them. Or maybe you had to do it this way because redeploying your VMs and changing the IP or Computer Name afterward will break the installed application. What ever reason you have to carry this exercise for you will need multiple isolated networks. Actually most organizations can quickly utilize thousands of these isolated networks, but using VLANs for that will just slow you down as you will have to request a new VLAN from your network team each time you deploy one of those applications. Your networking team will not like that and will be worried you deplete all their VLANs in no time. To resolve such a problem VMware has introduced VMware vCloud Director Network Isolation(vCDNI), which allowed you to take one VLAN and cut it into multiple isolated networks that simulate VLANs using Mac-in-Mac isolation. While vCDNI did the trick initially, it was VMware propriety and the networking gears were not aware of it. If you know what vCDNI is then VXLAN is kinda the next generation of vCDNI while being an open standard that networking manufacture will incorporate and enhance in their gears.

The main use in my opinion of VXLAN is being able to take a single VLAN and cut it on the fly in multiple isolated networks without being worried to run out of VLANs as VXLAN allow you to create up to 16.7 million VXLAN. The other beautiful part it can be automatically created and controlled by the software like vCloud Director without having to request it from the networking team. Though being understood by the networking gears will help accelerate it and make VXLAN more adaptable and manageable than vCDNI .

Another use of it for the near future is that you will be able to extend VXLAN across sites without the cost and trouble faced today when extending VLANs. While this is being marketed the most today, I believe the solution still need a bit of more enhancements before being a viable alternatives to stretched VLANS though I see this being ready in the real near future. The sad part which confuse most people trying to learn VXLAN is how much marketing are emphasizing on it being stretchable and make it seems as the main purpose of such technology where its more of the future state of it.

Seeing what VXLAN can help you achieve, I can see it playing a large part in the Software Defined DataCenter in particular Software defined Networking (SDN).

Below are few more detailed VXLAN articles that should give you more in depth knowledge of VXLAN if you require it:

VXLAN basics and use cases (when / when not to use it)  by Duncan Epping

VXLAN Deep Dive by Joe Onisick

Examining VXLAN by Scott Lowe

VXLAN Teaming Policy trade off how are you interacting with upstream network  by Prasenjit Sarkar

2199 VXLAN and the vDistributed Switch by Erick Sloof

Hope this help, & would love to hear your feedback .


  1. Hi Eiad – Thanks for sharing this post on VXLANs!


  2. Vaibhav Chopda says

    great post! I have been hammered by the marketing materials that say vxlan solves the scarce vlan problem but this is the first article i have read which really explains why it came to existence! Thanks for helping out to newbies like me!

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