-- IPV4 has how many addresses ~4.29 billion unique IP addresses To be precise: 2³² = 4,294,967,296 addresses And we are at the verge of exhausting that number. NAT is the answer to this problem., Now the Router is performing NAT functions as well. This will change the source address to the public IP address of the router NAT swaps the source, and destination addresses so that we can then use the public internet , It does not always happens on the router level sometimes it happens in the Proxy server