you are the network administrator for a single domain with three subnets. two subnets have all windows 10 computers. the conference room uses the third subnet. traveling salesmen come to the conference room and plug in their laptops to gain network access. you have configured a dhcp server to deliver configuration information to hosts on this subnet. dns is configured for dynamic updates. over time, you notice that the size of the dns database continues to grow. it is beginning to have an adverse effect on dns server performance. what should you do?