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VXLAN for dummies :-)

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What is VXLAN ?


VXLAN is Virtual Extensible LAN-- duh everyone knows that bit.

 


Well here's a bit more detail ...



 

A layer 2 network is essentially a single broadcast domain, typically one can implement using a generic network design or implement VLANs.

As one can imagine as we move into cloud computing era , with multi-tenants, there are scalability concerns with only having 4095 networks

 


Virtual Extensible LAN (VXLAN) is a network virtualization technology that attempts to alleviate the scalability concerns with larger environments.


 

 

How is it done ?

 

It uses a VLAN-like encapsulation technique to encapsulate MAC-based OSI layer 2 Ethernet frames within layer 3 UDP packets.

 

 

  1. -Basically picks up a network packet and adds another layer(UDP header) with a 24 bit-VXLAN ID.
  2. -UDP frame is padded with a 802.1Q VLAN tag correlating to a participating ESX-VMkernel Interface.
  3. -Each ESX host-VMkernel interface then becomes a Virtual tunnel Endpoint(VTEP) with VXLAN participants(Virtual Machines) behind it.
  4. -Hosts VMKernel interfaces communicate with standard VLANs and know of Virtual Machine(VXLAN) behind each other by monitoring ARP requests and updating their MAC tables.
  5. -Thus establishing communication between a source and destination VM.

 

Lo and Behold now we have 16 million logical networks not in thousands

 

Note that this is an effort to explain in laymans' term of what VXLANs are. There are more detailed explanations with packet flow that give a greater insight once this basic understanding is established.

 

Additional References:

 

https://blogs.vmware.com/vsphere/2013/05/vxlan-series-how-vtep-learns-and-creates-forwarding-table-part-5.html


-Cedric


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