PAT is also called overloading NAT. I don't understand why we need to use PAT? NAT alone is handling IPv4 addresses then why it is required to translate port also?Today's home wifi router use both NAT and PAT simultaneously which is also called NPAT. Your network will still work without PAT also then why PAT is used?
NAT: Network Address Translation; PAT: Port Address Translation
Network Address Translation (NAT) and Port Address Translation (PAT) both map IP addresses on an internal network to IP addresses on an external network. Which method of address translation you use depends on the types of networks that you are translating and the number of available IP addresses that you have.
Please see.