Rewriting application layer headers
The headers of HTTP and its typical payload, HTML or XML, often refer to domain names or IP addresses. For example, the Host: field in an HTTP header may be:
Host: www.example.com
and the HTTP body may contain XHTML with hyperlinks:
<a href=”http://www.example.com/index.php”>
Because of this, routing a packet while applying NAT at the lower TCP/IP layers of the packet can create inconsistencies with the HTTP layer unless you also rewrite the HTTP header of the packet. For that reason, when applying application layer content-based routing, you may also need to configure content rewriting — that is, rewriting of the application layer headers.
While rewriting the application layer to support content-based routing, you can also rewrite the HTTP layer of a packet for:
• aesthetic reasons (to make the URL more easily memorized by customers)
• security reasons (for example, to hide the URL structure of an application that would otherwise help attackers to fingerprint a vulnerable application)
To configure content rewriting rules, go to
Server Load Balancer > Content Rules > Content Rewriting Rules.
