Virtual Server creation & mapping

HTTP classes are replaced with policies in 11.4, and are much more robust than before. If you choose the iRule route though, here's what that may look like:

when HTTP_REQUEST {
    switch [string tolower [HTTP::host]] {
        "abc.com" {
            pool abc_pool
        }
        "xyz1.com" {
            pool xyz1_pool
        }
        "xyz2.com" {
            pool xyz2_pool
        }
    }
}

For each new request, assign a pool based on the incoming HTTP Host header.