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I have a snapt balancer with one front end listening on port 9055, attached to a backend with only one server at the moment (for testing) also listening on port 9055.

When I go to a browser and type: http://load-balancer-name:9055 the browser shows the page of http://back-end-server:9055 which shows the page I was expecting.

Once that the load balancer contacts the back end server, will the response from the server go directly back to the client, or will it go back to the load balancer, and the load balancer send it to the client?

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This depends on the implementation of the load balancer. Typically though, the request goes directly from the web server back to the client, bypassing the load balancer on the way back.

If you want to know for sure, do a packet capture on your load balancer (tcpdump), load it in Wireshark and step through the traffic. Or, you could capture the traffic on the web server and see if it sends the response to the load balancer, or back to the original client there.

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Hi Mark, I can't login to the load balancer, unfortunately is a gui appliance from snapt. But the client browser gets the original ip of the web server I am load balancing (backend). But you already answered that typically the response goes to the client bypassing the load balancer. I thought that was not the case. Thank you very much! – MisterWalrus Oct 19 '12 at 4:10
I strongly recommend you do a packet capture on your web server then an have a look at its destination addresses, because I can't guarantee that it's the same for every device. – Mark Henderson Oct 19 '12 at 5:27
I got tpcpdump running at the webserver and it shows periodic conversations with the load balancer and the full conversation with the client browser directly. Besides that, the client netstat -an only shows a brief connection to the load balancer and a longer ESTABLISHED connection directly with the web server. Thank you Mark – MisterWalrus Oct 19 '12 at 12:24

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