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New Member

CSS 11501 Load balancing slowness


We have a CSS 11501 unit connected to several servers for load balancing which has been running fine for over 12 months. Lately however we had been recieving complaints that our web pages have been loading slowly, sometimes 2-3 minutes to load a page. We have been unable to replicate the problem and it only happens to about a dozen users (so far). I am wondering if it is related to the CSS config? The servers are never under a load.

Here is what I have setup for a load balancing rule which has never changed from when I first installed it:-


content L3_Rule

advanced-balance sticky-srcip

add service HPServer1

add service HPServer2

balance aca

vip address xx.xx.xx.xx


Cisco Employee

Re: CSS 11501 Load balancing slowness

I would personally not recommend 'balance aca'.

I prefer 'balance leastconn'.

The main reason is because you don't know what balance aca will do.

But I do not think this is related to your problem.

Unless you can capture a sniffer trace showing the problem, I don't think will find out what is the problem by just looking at the config.



New Member

Re: CSS 11501 Load balancing slowness

The only problem with using "balance leastconn' is that we use session files on our web servers so wouldn't that confuse the client if suddenly the CSS moved that client's requests to a different server within the same session?

Also I'm concerned about the "advance src-sticky" whether we even need that or not. Main reason I left it there is because of http file uploads and sessions.


- Trevor

New Member

Re: CSS 11501 Load balancing slowness

Oops, another silly question, how do we do a "sniffer trace"?

- Trevor

Cisco Employee

Re: CSS 11501 Load balancing slowness

first, the 'balance aca' and 'balance leastconn' will both have the same problem that you describe.

That is, both of them do not guarantee that a connection belonging to the same ftp session is forwarded to the same server.

The, the solution to the problem that you describe is 'advanced-balance sticky-srcip'.

This means the CSS will create a sticky table based on src ip.

The same src ip will always be forwarded to the same server - whatever the balance method.

So, since it looks like you don't really know why you have ACA, I strongly recommend leastconn.

Finally, a sniffer trace is a capture of the traffic going through the CSS.

In this case, we would actually need 2 simultanous trace. One on the client side, to what is coming into the CSS and one on the server side to see what is coming out of the CSS.

Go to for a free sniffer.


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