how can I create custom DNS entries for my LAN while using bitdefender total security and box 2?

I want to setup custom DNS entries on the bitdefender box 2 such that my devices can resolve to LAN IP when they are connected through the bitdefender box 2 soho network.

note: the same name is also resolvable from the internet but pointing to my ISP provided public IP which, in turns has some ports forwarded to specific subsites....

something fairly common to dnsmasq.