Network Address Translation

External/Internal/

OVERLOADING

In Overloading, each computer on the private network is translated to the same IP address; that of the NAT external interface, but with a different port number assigned.

1. Private host generates an IP packet that gets sent to the NAT router. NAT removes the private IP address from the packet and puts the public IP address into the packet.

2. NAT appends a randomly assigned port number to the public IP Address.

3. NAT stores the private IP address and the port assigned in a table for future reference.

4. NAT forwards the packet to the public network.

5. When the host on the public network responds, NAT uses the table to see which private address the packet should go to.

6. NAT replaces the public address with the private IP address of the host that originated the communication and forwards the packet to the private network.

7. When the session is completed, the port is returned to the pool to be reassigned as needed.

STATIC

In Static NAT the computer with an IP address of 10.0.0.2 will always translate to 209.5.1.2.

DYNAMIC

In dynamic NAT, any computer on the private network will translate to an available address in the range from 209.5.1.2 to 209.5.1.50

209.5.1.2 to

209.5.1.50