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
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
Why should I be concerned?
Without state synchronization applications can break if there is a
the active to standby unit. FTP Sessions will be broken, Telnet
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
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?
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.
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