Block all dns record and allow only A record irule

When deploying GTM, the config guide recommendation is to use self or floating IP for listener.

the goal of this recommendation is to forward non wide IP requests to local Bind hosted on the F5 appliance.

if you don't want these requests to be forwarded to local Bind, you can create a listener on a different IP. it will create a virtual server. if you don't assign a pool to this listener, all requests not matching a wide IP will be dropped silently.