I am trying to create an advanced agent data filter for a blank "DNS Server 2" field, but all of my efforts have been fruitless.  Does anyone know if this is possible, and if so, how?

After that, I'd like to create a second filter where "DNS Server 1" does not begin with 192.168.* OR 172.16.* OR 10.* OR   Again, any pointers?

Thank you!