I want to assume that my local DNS servers retain a cache of the lookups for all external domains... .com , .mil , .edu, etc,etc that my PC clients request but these servers do not have and have to send a fetch for the answers. If these servers do retain a cache and I wish to stop them from retaining a cache....Should .. I go to my DNS\DHCP console, DNS tab, highlight the 'RootServerInfo' zone and then click on the SOA and change the Minimum TTL to 0 (zero)?

...or is there another way?

Also, am I correct in NOT setting either of my DNS servers as Authoritative or as a Designated Primary for the RootServerInfo zone?