DNS

[Zaid Dashti]

hello
i bought a domain, and i'm trying to host it using my machine in my home 
(just for learning how to host and DNS)

but i got a problem, when i use nslookup then i change the server to my DNS 
machine IP local network (by using another computer in the local network), 
it works fine, but when i use the IP of my internet account, i got time-out
why? how to solve it ?

thanks
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Zaid Dashti