Dns cache server error on like server:unknown

Hi Everyone,

I configured cache dns server on centos 7 , everything working fine like browsing and no latency on internet speed also even I am able dig the information of someother from server and client machine.
Issue is when i am trying to do NSLOOKUP from windows client it is showing like
server: unknown
Ip addr: instead of unknow it should show my server hostname .

could you please any one suggest me on this.

thanks in advance