Domain name access only

It is not clear what your requirement is.

Do you mean an iRule that ensure that the client cannot access the application via the IP address? If so, that is very simple - just check the HTTP Host header.

when HTTP_REQUEST {
    if { [string tolower [HTTP::host] ] != "" } {
        reset
    }
}

@Pete White:

  when HTTP_REQUEST {
if { [string tolower [HTTP::host] ] != "www.f5.com" } {
    drop

log [HTTP::host] }

Which string can expression all domain name , not work , you know ?

Try that

when HTTP_REQUEST {
    if { !([string tolower [HTTP::host] ] ends_with "company.com") } {
        reset
    }
}

OK. I meant that you should replace with the FQDN that your application is using.

I guess you are asking for an iRule that stops any requests with an IP address as the Host header.

when HTTP_REQUEST {
    if {[regexp {^(?:(\d{1,2})|(1\d{2})|(2[0-4]\d)|(25[0-5]))(?:\.((\d{1,2})|(1\d{2})|(2[0-4]\d)|(25[0-5]))){3}$} [HTTP::host]]} {
        reset
    }
} 

Note that regex is not very performant but this will check the host header against a regex for an IP address. You could consider using string match or the suggestion above by Stanislav if you know the domain that you want to use.