Introduction to Network Layer NAT and PAT

What is the purpose of NAT?

What type of mapping does Static NAT allow?

Which type of NAT provides a degree of security by hiding the inside IP addresses from the outside world?

In Dynamic NAT, how are unregistered private IP addresses mapped to registered public IP addresses?

What is the benefit of Dynamic NAT over Static NAT in terms of address configuration?

What happens if all inside global IP addresses are exhausted in a network?

What is the purpose of a timeout value in Dynamic NAT?

What is the main function of PAT (Port Address Translation)?

What is the range of port numbers used in PAT?

How does PAT enable multiple users to connect to the Internet with only one real global IP address?

Network Address Translation (NAT)

NAT translates private addresses to global addresses to solve the problem of IP depletion.
Private IP addresses are:
Class A: 10.0.0.0 – 10.255.255.255
Class B: 172.16.0.0 – 172.31.255.255
Class C: 192.168.0.0 – 192.168.255.255

NAT Addresses

Inside local addresses are assigned to inside devices and are not advertised to the outside (Private IP address of the host).
Inside global addresses are the addresses by which inside devices are known to the outside (Public IP address of the host).

NAT Concept

Inside Local (Private Address) is mapped to Inside Global (Registered Address).

Types of NAT

Static NAT: One-to-one mapping between local and global addresses, requiring one registered public IP address for every host on the network.
Dynamic NAT: Mapping unregistered private IP addresses to registered public IP addresses from a pool of available registered IP addresses.
PAT (Port Address Translation): Mapping multiple unregistered private IP addresses to a single registered public IP address, using different port numbers.

PAT (Port Address Translation)

Uses 16-bit port numbers (0 – 65535) to map multiple private IP addresses to a single public IP address.
Well-known ports: 0 – 1023
User-defined ports: 1024 – 65535
Allows hundreds or thousands of users to connect to the Internet using only one real global IP address.

This quiz covers the basics of Network Address Translation (NAT) in the network layer. It includes definitions, purposes, private IP addresses, and NAT addresses such as inside local addresses. Prepared by Dr. Mohammed A. Moharrum.