11501 load balance server in another site

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Mar 17th, 2009
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Dear Sir,

I have the below senario.

1) SiteA and SiteB are linked together by site-to-site VPN.

2) A pair of 11501 are installed in SiteA for load balancing.

3) SiteB are connected to Internet through SiteA. No direct Internet link in SiteB.

4) SiteA can access Internet directly.

Can I load balance web servers in SiteB with the 11501 in SiteA?


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Gilles Dufour Tue, 03/17/2009 - 08:48
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Yes you can.

You just need to make sure that the routing is not asymetric.

So, the response from the server must go through the CSS.

You may have to enable client nat on the css to guarantee this.


josephschung Wed, 03/18/2009 - 02:05
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Hi Gilles,

Which document will help me on this? Or do you have any example?


Syed Iftekhar Ahmed Wed, 03/18/2009 - 02:23
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As Gilles said you need to make sure that the return traffic from the real server should come back to CSS.

Your routing infrastructure should ensure that flow should be the following for both "real server in the same DC" & "Real Server in Different DC".

1. Client Traffic should hit the VIP configured on CSS.

2. CSS should forward the client request to the Selected Real Server.

3. Real Server's Response should reach CSS. (It should not go to Client directly)

4. CSS should send the response on Real Server's behalf.

As long as the above conditions are met you are fine. Step 3 is the key and becomes could become tricky for Remote Real Servers.


Syed Iftekhar Ahmed

josephschung Fri, 05/15/2009 - 00:51
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HI Syed,

External traffice arrive from port e1, and we would like to dedicate port e6 for a server farm. Thus, all traffice to server farm should go through port e6.

How can we control the traffic so that step 2 and step 4 go to port e6 only?



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