Configuring Static NAT for Any Network Scenario

Introduction

Network Address Translation (NAT) is a fundamental technique used in networking to translate private IP addresses to public IP addresses and vice versa. Static NAT is a method where a specific private IP address is mapped to a specific public IP address. 

Configuration Steps

Router Configuration

1. Enable NAT Service

   Router(config)#ip nat inside source static [inside-local] [inside-global]
   

   • Replace [inside-local] with the private IP address to be translated.
   • Replace [inside-global] with the public IP address to translate to.

2. Configure Interfaces

   Router(config)# interface [inside-interface]
   Router(config-if)# ip address [inside-ip-address] [subnet-mask]
   Router(config-if)# ip nat inside
   Router(config-if)# no shutdown
   Router(config-if)# exit
   
   Router(config)# interface [outside-interface]
   Router(config-if)# ip address [outside-ip-address] [subnet-mask]
   Router(config-if)# ip nat outside
   Router(config-if)# no shutdown
   Router(config-if)# exit
   

   • Replace [inside-interface] with the interface connected to the internal network.
   • Replace [inside-ip-address] and [subnet-mask] with the appropriate IP address and subnet mask for the internal interface.
   • Replace [outside-interface] with the interface connected to the external network.
   • Replace [outside-ip-address] and [subnet-mask] with the appropriate IP address and subnet mask for the external interface.

3. Configure Static Routes

   Router(config)# ip route [external-network] [subnet-mask] [next-hop-ip]
   

   • Replace [external-network] with the destination network.
   • Replace [subnet-mask] with the subnet mask of the destination network.
   • Replace [next-hop-ip] with the next-hop IP address to reach the external network.

4. Save Configuration

   Router# write memory
   

Verification and Testing

1. Check NAT Translations

   Router# show ip nat translations
   

2. Check NAT Statistics

   Router# show ip nat statistics
   

3. Perform Ping Tests

   SourceDevice> ping [destination-public-ip]
   

4. Check Routing Table

   Router# show ip route