Chapter 3

Configuring Advanced Expressions: Getting Started

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Which expression prefixes you can specify depends on the NetScaler feature. The following table describes the expression prefixes that are of interest on a per- feature basis.

Permitted Types of Expression Prefixes in Various NetScaler Feature

Feature

Types of Expression Prefix Used in the Feature

 

 

DNS

SYS, CLIENT, SERVER

Responder in Protection

HTTP, SYS, CLIENT

Features

 

Content Switching

HTTP, SYS, CLIENT

Rewrite

HTTP, SYS, CLIENT, SERVER, URL, TEXT,

 

TARGET, VPN

Integrated Caching

HTTP, SYS, CLIENT, SERVER

Access Gateway,

HTTP, SYS, CLIENT, SERVER, URL, TEXT,

Clientless Access

TARGET, VPN

Note: For details on the permitted expression prefixes in a feature, see the documentation for that feature.

Single-Element Expressions

The simplest type of advanced expression contains a single element. This element can be one of the following:

true. An advanced expression can consist simply of the value true. This type of expression always returns a value of TRUE. It is useful for chaining policy actions and triggering Goto expressions.

false. An advanced expression can consist simply of the value false. This type of expression always returns a value of FALSE.

A prefix for a compound expression. For example, the prefix HTTP.REQ.HOSTNAME is a complete expression that returns a host name, and HTTP.REQ.URL is a complete expression that returns a URL. The prefix could also be used in conjuction with operations and additional prefixes to form a compound expression.

Operations

In most expressions, you specify an operation on the data that the prefix identifies. For example, suppose that you specify the following prefix:

http.req.url

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Citrix Systems 9.2 manual Single-Element Expressions, Operations, Feature Types of Expression Prefix Used in the Feature