CCNA Network Address Translation (NAT) – LAB

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Here's a detailed lab guide for configuring Network Address Translation (NAT) for your CCNA exam preparation:

Objective:
Configure NAT (specifically PAT with overload) on a router to allow internal devices to access external networks using a single public IP address.

Hardware Requirements:
• Two routers with one serial port and two FastEthernet or Gigabit ports each
• One back-to-back DTE/DCE serial cable
• IOS version 12.x or later
• At least one PC running a terminal emulation program
• Cisco console kit

Network Diagram:
PC1 ---- R1 ---- R2 ---- Internet

Step-by-Step Configuration

Step 1: Initial Setup

(i). Erase any existing configurations on the routers and reload them.
(ii). Configure the hostname for each router:

Router> enable
Router# configure terminal
Router(config)# hostname R1

Step 2: Interface Configuration

(i). Configure the interfaces on R1:

R1(config)# interface serial0/1/0
R1(config-if)# ip address 192.1.1.1 255.255.255.252
R1(config-if)# no shutdown

R1(config)# interface gigabitethernet0/0/0
R1(config-if)# ip address 10.1.1.1 255.255.255.0
R1(config-if)# no shutdown

R1(config)# interface gigabitethernet0/0/1
R1(config-if)# ip address 148.1.1.1 255.255.255.0
R1(config-if)# no shutdown

(ii). Configure the interfaces on R2:

R2(config)# interface serial0/1/0
R2(config-if)# ip address 192.1.1.2 255.255.255.252
R2(config-if)# no shutdown

Step 3: Access Control List (ACL)

(i). Create an ACL to permit internal network traffic:

R1(config)# ip access-list standard 1
R1(config-std-nacl)# permit 10.1.1.0 0.0.0.255
R1(config-std-nacl)# permit 148.1.1.0 0.0.0.255
R1(config-std-nacl)# exit

Step 4: NAT Configuration

(i). Define the inside and outside NAT interfaces:

R1(config)# interface gigabitethernet0/0/0
R1(config-if)# ip nat inside

R1(config)# interface gigabitethernet0/0/1
R1(config-if)# ip nat inside

R1(config)# interface serial0/1/0
R1(config-if)# ip nat outside

(ii). Configure NAT overload:

R1(config)# ip nat inside source list 1 interface serial0/1/0 overload

Step 5: Verification

(i). From PC1, test connectivity:

ping 192.1.1.2

(ii). Verify NAT translations on R1:

R1# show ip nat translations

Expected Output:
You should see the NAT translations indicating that internal IP addresses are being translated to the external IP address for communication with the outside network.

This lab guide should help you get hands-on practice with NAT configuration, which is a crucial part of the CCNA exam.