Scenario 8.
A connection towards an external DNS server gets redirected to the internal DNS server.

Host 192.168.0.3 outputs a DNS query to the DNS server specified in resolv.conf. Network gateway intercepts DNS queries directed to port 53, not coming from the internal DNS server, and forwards them to the internal DNS server 192.168.0.2 (steps 1 and 2).
Suppose that the DNS server in the private LAN has not in cache the query just received: it then has to connect to an external DNS server, let's say 212.216.112.112, obtaining finally an answer (steps 3, 4, 5 and 6). Note that DNS response is depicted in violet. The following stage concerns the delivering of the DNS response first requested by 192.168.0.3 (steps 7 and 8). In blue color the path expected by the first machine, unaware of the redirection.

Communication details for DNS server redirection, gateway's point of view

DNS query is transparent from 192.168.0.3's point of view.