Cisco Cisco ACE Application Control Engine Module

By default, persistence rebalance is disabled. To enable the strict persistence rebalance feature, use the 
persistence-rebalance strict command in HTTP parameter-map configuration mode. The syntax of this 
command is as follows: 

For example, to enable the strict persistence rebalance feature, enter: 

host1/Admin(config)# parameter-map type http http_parameter_map

host1/Admin(config-parammap-http)# persistence-rebalance strict

To reset persistence to the default setting of disabled, enter: 

host1/Admin(config-parammap-http)# no persistence-rebalance

To revert to the persistence rebalance behavior that load balances successive GETs to the same server if 
the request results in load balancing that chooses the same Layer 7 class in the load-balancing policy, 
use the persistence-rebalance command.

This section describes the use of the new “\xST” metacharacter for regular expressions that are used as 
part of Layer 4 generic data parsing

.

It includes the following topics:

The “\xST” (STop) metacharacter is now available in software version A2(2.1) for all regular 
expressions (regexes) that are supported by the ACE. This new metacharacter has been provided for 
specific use cases that utilize the maximum parse length to terminate parsing. However, the “\xST” 
metacharacter is specifically designed for use by applications that involve the generic data parsing of a 
Layer 4 payload. 

If you intend to use the “\xST” metacharacter for regex matches on packets from protocols, we 
recommend that you use this metacharacter only for the following protocols in the generic data parsing 
of a Layer 4 payload:

SSL session-ID stickiness—To perform sticky hashing on the initial packets in an SSL handshake, 
allowing the ACE to stick the same client to the same SSL server based on the SSL session ID.

Financial Information eXchange (FIX) type ‘A’ Logon message—To define load-balancing criteria 
while setting up the outbound path of a connection.

In earlier releases of the ACE software, without the ability to include the “\xST” metacharacter in 
regexes, there are certain SSL session-id and FIX packets that may get stuck in the ACE HTTP engine 
and eventually time out the connection. The inclusion of the “\xST” metacharacter will now aid the ACE 
in properly load-balancing SSL session-id and FIX packets.

The “\xST” metacharacter has been added to software version A2(2.1) per CSCsh04655.