i have een question im trying to figure out how to get the internal ip's in a network

my ISP only gives me 1 ip adres zoo we have to buy a router if a want internet at more then 1 pc

i have all my card's at dynamic so my router is giving ip internal adres

i was wondering how to i get the internal ip's if i know the external adres

i tried scanning with nmap and other scanners but i cant figure it out


Modem ----> Router ----> 1 PC
2 PC
1 Laptop