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The Concept of VDC ( Virtual Device Context ) - Nexus Switches

 The Concept of VDC ( Virtual Device Context ) - Nexus Switches


Whenever you are talking about the Cisco datacenter environment in Nexus Switching, VDC is the first thing is in your mind. VDC ( Virtual Device Context ) is actually the separation of the single physical Nexus chassis into various different virtual chassis. So in simple words you can say that a single chassis divided into more than 2 chassis virtually to operate differently.

Audience # CCIE-Datacenter, Nexus Switching Experts, Network Experts, Network Engineers, Network Architect and Network Design Experts.

Before starting with the VDC ( Virtual Device Context ), you need to know where VDC works and how. The VDC feature can be enabled in the Cisco Nexus 7k Chassis. There are lot of models available in Cisco Nexus 7K Chassis and they are

  • Cisco Nexus 7004 Chassis
  • Cisco Nexus 7009 Chassis
  • Cisco Nexus 7010 Chassis
  • Cisco Nexus 7018 Chassis
All these Nexus datacenter chassis are equipped with this feature called as VDC ( Virtual Device Context ). So now question is why we required VDC ? How we create VDC in the enterprise network and how many VDC's can be created from the single Chassis.

Fig 1.1- VDC's in Nexus Chassis


Why we required VDC ? 
Well all these questions can be addressed differently as per the first question, VDC is generally used to lower the running costs of the physical chassis. Let us suppose you have 3 layer architecture in your datacenter environment, what are you laying there, Cisco Catalysts 6500 Chassis in the Core, Cisco Catalysts 6500 chassis in the distribution layer and at the access you can have various cisco chassis like 3800 series catalysts switches or 2960 switches or any other as per the design the requirement of the network. There is good amount if investments on Cisco 6500 Chassis or 6800 Chassis for this design recommendations. 

With the help of VDC ( a feature only used in Cisco Nexus 7k Chassis ) we have Single Nexus 7k Chassis and divided into 2 parts virtually and it acts differently on Core and distribution layers. So as per the good design you have the Nexus 7K Chassis in the peers, so you have 2 Physical Chassis and 4 Virtually Chassis representing Core and Distribution with vPC feature enabled and high capacity traffic from server to core. Similarly for the connectivity of the one datacenter to another datacenter, you can also create the another VDC from the same single Chassis named as OTV for the inter-datacenter connectivity.

Note: Make sure if there are 3 VDC's you are creating, it means they are 4 VDC's. How ?
  • 1 VDC : Core
  • 1VDC: Distribution 
  • 1 VDC : OTV 
  • 1 VDC : Admin VDC from where you actually creating all VDC's in the chassis.
How we create VDC in the enterprise network ?
It totally depends upon the need and the recommendation or the design of the enterprise network we required. If it's a standalone datacenter, then perhaps we required only 2 VDC's with 1 Admin VDC in the network or if there is any kind of the traffic is flowing with in two datacenter or one datacenter is shadowing the other datacenter then there will be another VDC named as OTV comes into picture. 

I knew your next question and that is What is OTV ? Well we will come up with OTV feature in the Nexus in the upcoming articles, but here we are totally discussing about the VDC feature in the Nexus Devices.

Fig 1.2- Cisco Nexus VDC Architecture


How many VDC's can be created from the single Chassis ?
This is interesting question, Well for this you need to know about the supervisor engine used in the Nexus Chassis or however if you are new to Nexus environment you can understand the supervisor concept from the Cisco Catalyst 6500 or 6800 Chassis. 

Nexus 7K can be used with the two Supervisor engines, Like if we are talking about the Nexus 7010 Chassis, it means it has 2 Supervisor engines and other 8 Slots are for I/O modules where you can use F or M modules. ( We will discuss F and M Modules in later article with the use cases )

So we have 3 kinds of Supervisor engines in Nexus Chassis can be used and they are :
  • SUP1
  • SUP2
  • SUP2E
What is the difference between these SUP Engines and how it impacts VDC's in the chassis ?
That is the  valid question, let me explain you these, These SUP engines are actually the evolution of the technology with the upgraded features and support, so we have the following Architecture with these SUP Engines

  • With the use of SUP 1 in Nexus Chassis, you can maximum create 4 VDC in Nexus Chassis
  • With the use of SUP 2 in Nexus Chassis, you can create 5 VDC's
  • With the use of SUP2e in Nexus Chassis you can create 9 VDC's
Hope with this article you are able to understand the concept of VDC's in the Datacenter environment. If still you have any queries please feel free to comment on the posts so that we can reply you back with your answers.