Configuring Port Address Translation (PAT) on Cisco Router by Using the Packet Tracer

Network Diagram:

Currently PC1 and PC2 cannot access the Web Server because they are using private IPv4 addresses, which are not allowed on the public network (Internet). To resolve this issue, PAT will be configured on the Gateway router. After this configuration, Gateway router will be able to map multiple private addresses (192.168.1.0/24) to a single public address (1.0.0.1) by using different ports and hence PC1 and PC2 will be able to access Web Server (2.0.0.2).

Background Preparation:
 First of all, enter the IP configuration on the end nodes (PC1, PC2, and Web server) according to network diagram. The figure below illustrates the process on PC1;

After entering the IP configuration on all end nodes, open the command line interface (CLI) of the Gateway router and configure its interfaces.

 Then configure the interfaces of ISP router.

 After setting-up IP configuration on both routers, configure a default route on Gateway router, pointing towards ISP router.

 Implementing PAT on Gateway Router:
After doing the background preparation, configure PAT on the Gateway router. This involves the following 3 steps:

• Specify “Fast Ethernet 0/0” as NAT inside and “Serial 0/0” as NAT outside interface.
• Identify the private IP addresses (192.168.1.0/24) that will be translated to public address (1.0.0.1) using an ACL.
• Activate PAT/NAT overloading.

 
Testing the Implementation of PAT:

After implementing PAT on the Gateway router, test it by sending ICMP, HTTP and FTP packets from internal hosts (PC1 and PC2) to Web Server. Then check NAT translations on the Gateway router by using “show ip nat translations” command.

  As it can be seen from the above image that the Gateway router is mapping private addresses (192.168.1.0/24) to public address (1.0.0.1) by using different ports, which means it is working properly.