How to Examine NAT on a Wireless Router?

Network Address Translation (NAT) involves switching the source and destination IP addresses as well as the port numbers. By hiding private network address ranges, address translation lessens the necessity for IPv4 public addresses. Typically, routers or firewalls carry out this process.

Example of NAT:

A web page request is made to an internet server by a host. The source address of the request must be altered by the router since Host A utilizes a private IP address, which is not routable on the Internet. After receiving the request, the router modifies the packet’s source IP address to be its own public IP address before sending it to the server. After receiving the packet, the server responds to the router. After receiving the packet, the router modifies the destination IP addresses to include Host A’s private IP address before sending the message to the host.

Examine NAT on a Wireless Router:

To examine NAT on a Wireless Router follow the below steps:

Step 1: Check the settings for gaining access to a remote network.

1. One PC should be added, and it should be a straight-through cable to the wireless router. Before proceeding to the next stage or choosing Fast Forward, wait for all link lights to turn green.
2. Select Desktop on the computer. Decide on IP Configuration. To allow each device to receive an IP address from the wireless router’s DHCP server, click DHCP.
3. Take note of the default gateway’s IP address. When finished, close the IP Configuration.
4. Open a web browser and type the default gateway’s IP address into the URL field. When prompted, enter the details of username and password as admin.  
5. Select the Status option from the menu in the top right corner. When decided, the Router sub-menu page is displayed.
6. Scroll down to the Internet connection option on the router page. The ISP’s address was used to assign this IP address. If 0.0.0.0 displays instead of an IP address, shut the window, wait a few seconds, then try again. The wireless router is now requesting an IP address from the DHCP server of the ISP.

The address displayed here is the one given to the wireless router’s Internet port.

Step 2: Check the settings for gaining access to the internal network.

1. In the Status sub-menu bar, select Local Network.
2. Scroll down to look at the data for the local network. The internal network’s address is as follows.
3. Continue scrolling down to look at the DHCP server details and the range of IP addresses that can be given to linked hosts.
4. The wireless router setup window should be closed.

Step 3: Connect up 3 computers with the wireless router.

1. Connect the wireless router to the additional three PCs using straight-through wires. Before proceeding or pressing the Fast Forward button, wait for all link lights to turn green.
2. Select Desktop on every PC. Opt for IP Configuration. To allow the wireless router’s DHCP to assign an IP address to each device, click DHCP. Once finished, exit IP Configuration.
3. Select Command Prompt and run the ipconfig /all command to check the IP configuration of each device.

These devices will be given a private address, please note. NAT translation is necessary because private addresses cannot travel across the Internet.

Step 4: View the wireless router’s NAT translation.

1. Select the Simulation tab in the lower right-hand corner to launch simulation mode. The Simulation tab, which includes a stopwatch icon, is situated adjacent to the Real-time tab.
2. Create a Complex PDU in Simulation mode to view traffic:
   1. Click Show All/None in the Simulation Panel to make all events invisible. After that, click Edit Filters and choose the TCP and HTTP checkboxes under the Misc tab. Once finished, shut the window.
   2. By selecting the opened envelope in the upper menu, you can add a Complex PDU.
   3. Select a PC by clicking on it to make it the source.
3. In the complicated PDU window, adjust the following values to specify the Complex PDU settings:
   1. The HTTP setting should be decided under PDU Settings > Select Application.
   2. To designate the destination device, click the ciscolearn.nat.com server link.
   3. Enter 1000 as the Source Port.
   4. Select Periodic under Simulation Settings. The Interval should be 120 seconds.
   5. In the window for creating complex PDUs, click Create PDU.
      
4. To unlock the simulation panel from the PT window, click twice on it. By doing so, you can reposition the simulation panel to see the whole network topology.
5. Click Play in the simulation panel to watch how the traffic moves. By moving the play control slider to the right, the animation can be speed up.

Note: When the warning “Buffer Full” appears, click “View Previous Events.”

Step 5: View the packet header data that was sent across the network.

• Look at the packet headers that were transferred between the PC and the web server.
• Double-click the third line down in the event list in the Simulation Panel. This causes an envelope, which stands in for that line, to appear in the work area.
• To examine the header and packet information, click the envelope in the work area window.
• Select the tab for Inbound PDU information. Look up the source (SRC) and destination IP addresses in the packet metadata.
• Select the tab for Outbound PDU information. Look up the source (SRC) and destination IP addresses in the packet metadata. Note how the SRC IP address has changed.
• To view those headers at various points in the process, click through additional event lines.
• Click Check Results to review your work after finishing.