Static NAT
Network Address Translation (NAT) is the process of changing a private IP address (which cannot route on the internet) into a public IP address (which can).
Static NAT is the simplest version of this. It is a permanent, one-to-to-one (1:1) mapping between a single private IP and a single public IP.
1.When do you use it?
Section titled “1.When do you use it?”You use Static NAT almost exclusively for inbound traffic. If you have a Web Server, an Email Server, or a VPN Gateway inside your network, the outside world needs a reliable, unchanging public IP address to connect to it. You statically map that server’s private IP to a public IP.
2.Configuration
Section titled “2.Configuration”The Scenario: You have a Web Server with a private IP of 192.168.10.50. Your ISP gave you a public IP of 203.0.113.5. Your router connects to the LAN on GigabitEthernet0/0 and to the internet on GigabitEthernet0/1.
Step 1: Create the Translation Rule
Section titled “Step 1: Create the Translation Rule”Router(config)# ip nat inside source static 192.168.10.50 203.0.113.5Step 2: Define the Inside Interface
Section titled “Step 2: Define the Inside Interface”Router(config)# interface GigabitEthernet0/0Router(config-if)# ip nat insideStep 3: Define the outside Interface
Section titled “Step 3: Define the outside Interface”Router(config)# interface GigabitEthernet0/1Router(config-if)# ip nat outside