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New Member

CSS 11051 Stateful Failover

We have received a note concerning stateful failover of the CSS series of products, where the CSS 110XX series doesn't support stateful failover, however the CSS 115XXX will. Here is the digest of the message;

On 3/6, Hosting Engineering and Operations issued an alert regarding the

CSS 11000 load balancer. This is an update to that alert.

Since that time, we have experienced another hardware failure of this

model device.

In response to this situation, the following has occured:

* Platform Engineeringis in the process of removing the CSS 11000

from the SOE. Itis on target to be removed in April.

* Operations hasre-inforced our escalation procedures with CISCO.

Qwest is to beissued a RMA immediately for this model.

* For newconfigurations including a CSS 11000, CCAR will require

an Individual CaseBasis (ICB) review and approval.

* For existing premiumand above customers whoes configurations

include a CSS 11000, HostingOperations is planning to replace them with

compatible device. These changes have been pre-approved by CCAR as long


* the networktopology remains the same

* redundancy ispreserved

* CCAR gets notifiedof the replacement model so we can update our


* For existing basicand enhanced customers, we are drafting a

communique that alerts them tothe performance issues exerienced by Qwest

and providing suggestedalternative solutions.

In response to recent questions from the field.....

Stateful failover with redundant CSS 11000 Series Load Balancers:

The Bottom Line: Cisco CSS 11000 Series Load Balancers do not support



Will Cisco ever support this?: Yes, this is supported in the CSS 11500


known as Adaptive Session Redundancy (ASR)

I need this today, what can I do?: Choose an alternative product. The


load balancers support this functionality.

What is stateful failover anyhow?

Stateful failover is a technology that can maintain state information


the active load-balancer and the standby load-balancer. This state


can include: persistence mapping, telnet sessions, ftp sessions, tcp


state, etc...

Why should I be concerned?

Without state synchronization applications can break if there is a

failover from

the active to standby unit. FTP Sessions will be broken, Telnet

sessions will

be broken, and most importantly persistence state mapping will be lost.

What do I need to listen for to determine if stateful failover is


1. E-commerce applications that require persistence mapping.


mapping will keep a client session mapped to the same server for a


amount of time. This is often important with shopping cart and other



2. Long-lived sessions. Whether they are planning to transfer large

files via

FTP or long-lived telnet sessions. Anytime a connection will be

required for a

long time and starting over is not an acceptable condition, then


failover is important.

Does this sound correct or is this a bunch of hot air?

New Member

Re: CSS 11051 Stateful Failover

Yes. Stateful failover, or ASR as it is sometimes called, is available on the CSS 11500 and Catalyst 6500 Content Switch Modules (CSM) load balancing platforms. It is not supported on the CSS 11000 due to architectural limitations of that platform.

Stateful failover is available on these Cisco platforms today.