Step-by-Step Guide to Configuring NAT in Cisco Packet Tracer with Port Address Translation (PAT)
Understanding Network Address Translation (NAT) and its subset, Port Address Translation (PAT), is crucial for any network administrator. This guide provides a detailed step-by-step process to configure PAT in Cisco Packet Tracer, which simplifies the concept of NAT. This tutorial assumes that you have a basic understanding of network terminologies and are familiar with the Cisco Packet Tracer environment.
Introduction to NAT and PAT
Network Address Translation (NAT) is a method used to translate IP addresses for communication within a network. It helps in conserving public IP addresses and maintains anonymity. PAT, a specific form of NAT, allows multiple internal devices to share a single public IP address while maintaining their individual identities through port numbers.
Setting Up the Environment in Cisco Packet Tracer
Begin by opening Cisco Packet Tracer and setting up the environment according to the diagram provided:
Draw two local area networks (LANs) and label them as LAN1 and LAN2. Place two routers (Router1 and Router2) so that each router connects to one LAN and the other router.Configuring the Routers for NAT and PAT
Next, configure Router1 and Router2 to act as routers with NAT and PAT enabled. Follow the steps below:
Step 1: Assign IP addresses to the interfaces
Assign the following IP addresses to the interfaces:
Router1 Interface for LAN1: 192.168.1.1/24 Router1 Interface for LAN2: 192.168.2.1/24 Router2 Interface for LAN1: 192.168.1.2/24 Router2 Interface for LAN2: 192.168.2.2/24Step 2: Enable NAT on Router1 and Router2
Enable NAT on Router1 and Router2 using the following commands:
Router1(config)# ip nat inside source list 1 interface GigabitEthernet0/0 overloadRouter2(config)# ip nat inside source list 1 interface GigabitEthernet0/0 overload
Step 3: Create Access Lists for NAT
Create access lists to ensure that only specific traffic is translated:
Router1(config)# access-list 1 permit 192.168.1.0 0.0.0.255Router2(config)# access-list 1 permit 192.168.2.0 0.0.0.255
Step 4: Apply NAT to LANs
Apply the NAT configuration to the LANs using the following commands:
Router1(config)# ip nat inside source list 1 interface GigabitEthernet0/0 overloadRouter2(config)# ip nat inside source list 1 interface GigabitEthernet0/0 overload
Step 5: Enable the Interfaces for NAT
Enable the interfaces of Router1 and Router2 for NAT by specifying the inside and outside interfaces:
Router1(config)# interface GigabitEthernet0/0Router1(config-if)# ip nat insideRouter1(config)# interface GigabitEthernet0/1Router1(config-if)# ip nat outside
Router2(config)# interface GigabitEthernet0/0Router2(config-if)# ip nat insideRouter2(config)# interface GigabitEthernet0/1Router2(config-if)# ip nat outside
Testing PAT Configuration
To verify the PAT configuration, perform the following actions:
Step 6: Configure and Test Communication Between LANs
Assign IP addresses to the hosts in LAN1 and LAN2 and configure them to communicate through the routers:
Host1 in LAN1: 192.168.1.2/24 Host2 in LAN2: 192.168.2.2/24Host1(config)# ip address 192.168.1.2 255.255.255.0Host2(config)# ip address 192.168.2.2 255.255.255.0
Step 7: Ping to Verify PAT
Perform a ping test from Host1 to Host2 to verify that PAT is working correctly:
Host1# ping 192.168.2.2
Check the output to confirm that the ping is successful.
Verifying PAT with Show Commands
After configuring PAT, use the show ip nat translations command to see the NATted traffic:
Router1# show ip nat translations
This command will display the NAT translations, showing the source IP and port numbers being translated to the global (outside) address and ports. This output is crucial for debugging and understanding the NAT process.
Conclusion
This step-by-step guide demonstrates how to configure and verify Port Address Translation (PAT) in Cisco Packet Tracer, simplifying the concept of NAT for educational purposes. Through this process, you can gain a deeper understanding of how NAT and PAT work and apply this knowledge to real-world network configurations.