•Private IP network is an IP network that is not directly connected to the Internet
•IP addresses in a private network can be assigned arbitrarily.
–Not registered and not guaranteed to be globally unique
•Generally, private networks use addresses from the following experimental address ranges (non-routable addresses):
–10.0.0.0 – 10.255.255.255
–172.16.0.0 – 172.31.255.255
–192.168.0.0 – 192.168.255.255

•NAT is a router function where IP addresses (and possibly port numbers) of IP datagrams are replaced at the boundary of a private network
•NAT is a method that enables hosts on private networks to communicate with hosts on the Internet
•NAT is run on routers that connect private networks to the public Internet, to replace the IP address-port pair of an IP packet with another IP address-port pair.