DNS config question - block some sub-domains

["Roger Vicker, CCP" <rv-tech@xxxxxxxxxx>]

I have some mid-level managers that have legitimate authority to bypass
the firewall content filters. However,  the logs are showing that  they
have been abusing it to play online streaming radio content. (Upper
management defines it as abuse due to the bandwidth consumption)

The streaming content comes from a specific sub-domain (abc.def.com) and
I would like to change the configuration of the DNS (on the IBM i V5R4)
to poison (point to 127.0.0.1) the sub-domain but have the rest of the
domain (def.com and *.def.com) still get resolved normally.

I can setup the poisoned sub-domain (new zone for the base domain...)
but I haven't figured out how to set that everything else in the domain
continues to get forwarded for resolution.

Are there any FAQs or guides available for this? Especially ones that
can be followed with the IBM i GUI implementation of BIND configuration?

Roger Vicker, CCP