Modifying headers gives control over how HTTP functions. The LoadMaster can add, delete, and replace HTTP headers, including URL modification. This is done on a per Virtual Service basis and can be used for request and/or response headers.

Header modification can be used to add identifying information to incoming requests. For example, if the LoadMaster is offloading SSL, the traffic back to the server is usually HTTP plain text. Normally, the server does not know that this had come in on SSL originally. To help identify this traffic as SSL originating, a header such as SSL_Offload: Yes can be added.

Another reason you may use a header modification rule is to delete/modify sensitive information returning from the server, such as operating system or web server version.