Cisco 11501 load balancing

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Mar 8th, 2010
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Hi!


I have configured two Cisco CSS 11501 in Active/Stanby mode for load balancing operations on two servers. The two servers are configured on a cluster mode.

The system is working but there is an issue that one of the servers is getting more requests than the other. This is causing the server to have a higher utilisation and this is slowing down its performance.

Is this occuring because of the load balancing algorithm I have used?

I have checked and both servers have a weight of 1.


Please find attached the configurations, topology and outputs.


Thanks and regards,


Alvin

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Sean Merrow Mon, 03/08/2010 - 06:11
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Hi Alvin,


Your configuration looks fine, but you shouldn't expect to see the same number of connections on each server.  The reason for this is that you are using sticky.  Sticky will skew the results of your load balancing in two ways:


  1. Once a client come into the CSS for the first time, it will be load balanced to one of the two servers.  All subsequent connections from that same client (source IP address) will also be sent to that same server regardless of the number of current connections on that server (you are using leastconns).
  2. I noticed that your two servers each have many state transitions.  This means that they have failed keepalives.  If one of the two servers fails keepalives, then while that server is down and removed from the load balancing algorithm, all new client connections will be load balanced to the healthy server.  Now, even when the failed server comes back online as noticed by passing keepalives, those clients stuck to the healthy server will remain stuck to that server even though the second server is now back online.


So looking at the output you provided, I don't see anything out of the ordinary.


Hope this helps,

Sean

net buzz Mon, 03/08/2010 - 11:43
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Thanks Sean.


But I am wondering, is there any change that can be done to the configurations to optimise the load balancing operations?



Regards,


Alvin

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