how to send NXDOMAIN with BigIP DNS

Hi friends,

I have a question. A customer would like to manipulate some DNS responses using F5 DNS having the following use cases:

1. Change the DNS Response IP (to a public IP)
2. Change the DNS Response to NXDOMAIN (for IP addresses which should not be published)

I thought about the following iRule to create the 1st use case:

when DNS_REQUEST {

    if { [DNS::question name] equals "fqdn.of.customer" }{

      DNS::answer insert "[DNS::question name]. 3600 [DNS::question class] [DNS::question type] 1.2.3.4"

      DNS::return

    }

}

Any idea what I have to use to return a NXDOMAIN?

DNS::answer insert "???"

Do you see a simpler approach? (mid Term we will implement different DNS views).

Thanks,

Rolf