Network address Translation:NAT Understanding


Network address Translation:
Network address translation is a method of mapping one IP address into another by modifying network address information in the IP header of packets while they are in transit across a traffic routing or Layer 3 device. As we know that private address are not routable on the internet. We can only communicate with public address on the internetSo with the help of NAT process, we can translate a private address into public addresses.


The below following table lists the address ranges as specified in RFC 1918 that we can use as internal private addresses. These will be our inside the LAN addresses addresses that we will have to be translated into public addresses that can be routed across the Internet. These below addresses are not allowed to be routed onto the public Internet.

Private Addresses
Class
RFC 1918 Range
CIDR Prefix
A
10.0.0.0–10.255.255.255
10.0.0.0/8
B
172.16.0.0–172.31.255.255
172.16.0.0/12
C
192.168.0.0–192.168.255.255
192.168.0.0/16

Dynamic Network Address Translation:
Dynamic Address Translation (Dynamic NAT) maps unregistered i.e private IP addresses to registered i.e. public IP addresses from a pool of registered (public) IP addresses.

PAT: Many Private to One Public Address Translation:

PAT maps multiple private IP addresses to a single  public IP address i.e many to one using different ports. This is also known as overloading or overload translations. By the use of  PAT or overloading, thousands of users can be connected to the Internet by using only single  real registered public IP address.

Static NAT: One Private to One Permanent Public Address Translation:
Static Address Translation (Static NAT) allows one to one mapping between local private and global public IP addresses.

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