[MacBook Air] <--> [Mac Mini Server] <--> [Fritz!Box] <--> internet

[MacBookAir]    -> [MacMiniServer] : #1 : Ask for github.com
[MacMiniServer] -> [Fritz!Box]     : #2 : Ask for github.com
[MacMiniServer] -> [OtherDNS]      : #3 : Ask for github.com
[MacMiniServer] <- [Fritz!Box]     : #2 : reply with github.com IP
...