11.3 Configuring NAT
11.3.1 Static NAT configuration

At a minimum, IP routing and appropriate IP addresses must be configured on the router before starting the NAT configuration. To enable basic, static local IP address translation, perform the following steps:

  1. Define the static addresses by using the ip nat inside source static local-ip global-ip global configuration command, as shown in Table . To remove the static translation, use the no form of this command.

  2. Enable NAT on at least one inside and one outside interface by entering interface configuration mode and entering the ip nat {inside | outside} command.

Only packets moving between inside and outside interfaces can be translated. For example, if a packet is received on an inside interface but is not destined for an outside interface, it will not be translated.

Example shows a sample static NAT configuration. The corresponding topology is shown in Figure .
Lab Activity    
  Our small company has recently been assigned the network number 206.222.222.0 by ARIN. Previously the company was using a private IP address on the internal network. Now that the company is going to be connected to the Internet, we need to either go to each and every workstation and configure it with a new IP address, or to use some kind of IP address translation at the router. For security reasons our company does not want the computers to be directly on the Internet, using real IP addresses. Since our company only has a limited number of computers, we have decided to use static network address translation. It is our job to configure the ISDN connection and implement the address translation.