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East-West traffic

Hi expert


I am new in data center. What I know about East-West traffic is traffic between server and server in data center.

But, why kind of traffic is this? Why the data need to be send from one server to another server? Could someone give some example situation?

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Re: East-West traffic



In Data Center, we have lot of applications/services installed related to Organization needs. Typical example includes Microsoft Infrastructure where in Data Center you will see Microsoft Active Directory Servers, Exchange Servers, data base servers. These servers need to communicate with each other, for example Exchange need to communicate with Active Directory for User Authentication. There might be many applications that need authentication from Active Directory. So these traffic are east-to-west traffic.  This is just simple example, there will be lot of applications in DC that requires communication with each other.


In a typical design, we need to protect and control east-to-west traffic by placing a Firewall in the data center. Firewall will be default gateway for those applications.


In Cisco new Software define DC, we control the East-to-West traffic using Cisco ACI Contracts.

VIP Mentor

Re: East-West traffic

It all depends on how your network design.


Do you have a Firewall between, then the trick is different here, you need to have a common interface to exchange routes (since ASA struggle here).


DC  Environment always have in and out traffic most of the time, but sometimes (most of the time required east-west traffic)

in traditional DC nexus, you need to maintain different method as suggested above (common interface).


In the case of ACI, this was overcome in a different ways.





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Re: East-West traffic

Hi @Anwar Safian,

The usual analogy for East-West traffic is a "3 tier application". Let's say that:

  • Server 1 runs the Web tier
  • Server 2 runs the App tier
  • Server 3 runs the Database tier

Some a very high level overview of the communication process is:

  • Some remote user initiates a request to Server 1-Web tier. This traffic enters the Data Center's network. Because this traffic originates from outside the Data Center network, we call it "North-South" traffic.
  • Once the request has hit Server 1-Web tier, this Server needs to contact Server 2-App tier to further process the request. Since this communication is now originated from inside the Data Center network to another server inside the Data Center network. We call it "East-West" traffic.
  • Server 2-App repeats the same process, it contacts Serve 3-Database to full-fill the request. This is again East-West traffic because of the same reason.
  • The response is in the opposite direction, Server 3-Database to Server 2-App to Server 1-Web.
  • It is Server 1-Web traffic who finally sends the response out of the Data Center Network to the remote user. For the purpose of this explanation, we may call it "South-North" traffic.

This is just an analogy. Traffic can be either type TCP or UDP. It all depends in the specifics of the application.

I hope this helps.

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