NAT,PAT is the answer.
thanks to ipv4 deficit, the classful ip addressing was scrapped and ip addresses were subnetted and heirarcially assigned based on geographical location.
so say your country A is assigned with IP range - 11.0.0.0/8
if there are 4 major ISPs operating in your country , the IP is subnetted to be
11.0.0.0/11
11.32.0.0/11
11.64.0.0/11
11.96.0.0/11
.
.
.
now each ISP has its own mushroom ISP who burrows IP addresses and each IP address gets subnetted further.
Not many home customers are lucky to have such IP addresses assigned to themselves - these IP addresses are known as public IPs. ISP mostly assign a private IP to each of its customer
customer1 : 192.168.3.9———|
|______2345_ISP___(……)
customer2 : 192.168.3.10———————4532_ISP___(….)
1.you send a http get to google
2. src address : 192.168.3.9 dst address : google IP
3. ISP : 192.168.3.9 is translated to ISP <public IP:2345>, similarly custoemr 2 IP is translated to ISP <Public IP:4532>, It has to be remembered that packets with public IPs are considered valid packets, packets cannot have an IP as prvte IP when going into wild.
4. google replies back to your request, src addr :google IP dst address: <ISP IP:2345>
5. your ISP receives the packet and maps the ISPI:2345 back to your IP (192.1.68.3.9) and routes the packet.
, you can look up internet for more explanation on Network Address Translation and Port Address Translation, also download wireshark and send across http requests to remote servers to check packets.
I hope this answers your question
#-Link-Snipped-# : that title was funny 😁
