Need some help trying to apply an iRule

Assume you have associated an HTTP or FastHTTP profile with the Virtual server? Default setting is none. If not, then you cannot use HTTP_REQUEST event and Layer 7 commands.

On Performance Layer 4 virtual server you might use CLIENT_ACCEPTED event, but depends on what the iRule does. With Performance Layer 4 you cannot use Layer 7 commands in the iRule. If you must, then you might use Performance HTTP virtual server.