Knowledge Base

What is NAT?

NAT (Network Address Translation) is a network addressing technique that converts private IP addresses in a network to a single public IP address. This allows devices on the local network to access the internet through a single public IP address. The main purpose of NAT is to alleviate the IPv4 address shortage and protect local networks from external attacks. It also simplifies network management and provides flexibility in IP address changes.

Basic Operating Principle:

• A device on the local network sends a request to the internet. This request reaches the NAT device along with the device's private IP address and port number.
• The NAT device receives this request and replaces the device's private IP address and port number with its own public IP address and a different port number.
• The modified request is sent to the internet.
• The response from the internet reaches the NAT device.
• The NAT device replaces the destination IP address and port number of the response with the private IP address and port number of the device that sent the original request.
• The modified response is sent to the device on the local network.

Advantages:

• IP Address Conservation: Allows multiple devices to access the internet through a single public IP address.
• Security: Protects local network devices from external attacks by hiding their IP addresses.
• Flexibility: Simplifies IP address management in network topology changes.

Disadvantages:

• Performance Issues: NAT processing can affect performance by processing network traffic.
• Application Compatibility: Some applications may not be compatible with NAT or may require special configurations.
• Complexity: Can complicate network configuration.

What is an IP Mask and How Does it Relate to NAT?

An IP mask (or subnet mask) is a number that specifies which part of an IP address represents the network address and which part represents the device address. The IP mask helps devices on a network understand which network they belong to and determines whether devices are on the same network.

IP Mask and NAT Relationship:

NAT is commonly used in local networks that use private IP address ranges (e.g., 192.168.x.x, 10.x.x.x). These private IP addresses cannot be directly routed over the internet. The NAT device provides internet access by replacing these private IP addresses with a public IP address.

The IP mask helps the NAT device understand which IP addresses are private and which IP addresses are public. For example, if a NAT device is using the 192.168.1.0/24 network (where /24 represents the 255.255.255.0 IP mask), it knows that IP addresses between 192.168.1.1 and 192.168.1.254 are private and require NAT processing.

Example Scenario:

Let's consider a home network. The modem/router functions as a NAT device. The modem obtains a public IP address from the Internet Service Provider (ISP). Devices in the house (computer, phone, tablet, etc.) have private IP addresses in the 192.168.1.x address range. When these devices want to access the internet, they send their requests to the modem/router. The modem/router replaces the source IP addresses of these requests (192.168.1.x) with its own public IP address and sends them to the internet. It also translates incoming responses in the same way, directing the destination IP address to the private IP address of the relevant device.

IP Mask Examples:

• /24 (255.255.255.0): The most commonly used IP mask. Allows for 254 devices in a network.
• /16 (255.255.0.0): Used for larger networks. Allows for 65,534 devices in a network.
• /8 (255.0.0.0): Used for very large networks. Allows for 16,777,214 devices in a network.

What are the NAT Types?

NAT (Network Address Translation) is divided into various types according to different needs and scenarios. The most common NAT types are:

• Static NAT: Always maps a private IP address to the same public IP address. It is often used for servers.
• Dynamic NAT: Temporarily assigns one of the public IP addresses in a pool to the requesting private IP address.
• PAT (Port Address Translation) / NAT Overload: Maps multiple private IP addresses to a single public IP address. This is the most commonly used NAT type and is often used in home and small office networks. It distinguishes different devices using port numbers.
• Full Cone NAT: After a device on the internal network sends a request to any address on the external network, any device on the external network can reach this device on the internal network via the previously used IP address and port.
• Restricted Cone NAT: After a device on the internal network sends a request to a specific address on the external network, only that address on the external network can reach this device on the internal network via the previously used IP address and port.
• Port Restricted Cone NAT: Similar to Restricted Cone NAT, but additionally, the device on the external network must use the same port.
• Symmetric NAT: When a device on the internal network sends a request to different addresses on the external network, a different port number is used for each request. This NAT type is the most restrictive NAT type.

Comparison Table:

How to Configure NAT? (Step-by-Step Instructions)

NAT configuration varies depending on the model and brand of the device used (router, firewall, etc.). However, the general steps and principles are similar.

Step 1: Accessing the NAT Device

1. Open your web browser.
2. Type the IP address of the NAT device into the address bar (e.g., 192.168.1.1 or 192.168.0.1).
3. Enter your username and password (default information is usually found in the device's user manual).

Step 2: Accessing NAT Settings

1. Find a section such as NAT, Firewall, Security, or Advanced Settings.
2. You can find NAT-related settings under this section.

Step 3: Choosing the NAT Type (Static, Dynamic, PAT)

Select the NAT type according to your needs:

• Static NAT: Use this option if you want to assign a fixed public IP address to a specific device, such as a server.
• Dynamic NAT: Use this option if you want to dynamically assign public IP addresses to a group of devices.
• PAT (NAT Overload): Use this option if you want to allow multiple devices in your home or small office network to access the internet through a single public IP address. This is the most commonly used method.

Step 4: Static NAT Configuration (Example)

1. Select the Static NAT option.
2. Enter the internal IP address (the private IP address of your server).
3. Enter the external IP address (the public IP address to be assigned to your server).
4. Specify the protocols (TCP, UDP) and ports (80, 443, etc.).
5. Save and apply.

Step 5: Port Forwarding Configuration (for PAT)

If you are using NAT, you may need to forward specific ports to specific internal IP addresses. This is called port forwarding.

1. Find the Port Forwarding section.
2. Add a new rule.
3. Enter the service name (e.g., HTTP, HTTPS, FTP).
4. Enter the internal IP address (the private IP address of the device to be forwarded).
5. Enter the external port range (e.g., 80-80) and the internal port range (e.g., 80-80).
6. Select the protocol (TCP, UDP, or Both).
7. Save and apply.

Example Port Forwarding Rule:

To forward port 80 (HTTP) to address 192.168.1.10:

• Service Name: HTTP
• Internal IP Address: 192.168.1.10
• External Port: 80
• Internal Port: 80
• Protocol: TCP

Step 6: Saving and Applying Settings

1. Check all settings and save.
2. You may need to restart the device.

Important Notes:

• NAT configuration can affect the security of your network. Incorrect configurations can lead to security vulnerabilities.
• When port forwarding, only open the necessary ports. Leaving unnecessary ports open increases the security risk.
• Read your device's user manual carefully and follow the manufacturer's recommendations.

Common Problems and Solutions Related to NAT

Some common problems may arise during the use of NAT (Network Address Translation). These problems are usually caused by configuration errors, application incompatibilities, or firewall settings.

1. Internet Connection Problems:

• Problem: Devices cannot access the internet or the connection is slow.
• Reasons:
  • Incorrect NAT configuration.
  • DNS server issues.
  • ISS (Internet Service Provider) issues.
• Solutions:
  • Check the NAT configuration and make sure it is correct.
  • Check the DNS server settings (use the DNS servers provided by the ISS or public DNS servers such as Google DNS (8.8.8.8, 8.8.4.4)).
  • Restart the modem and router.
  • Contact the ISS.

2. Application Compatibility Issues:

• Problem: Some applications (e.g., online games, VoIP applications) are not working or not working properly.
• Reasons:
  • NAT is not compatible with some applications.
  • The necessary ports have not been forwarded.
  • UPnP (Universal Plug and Play) is disabled.
• Solutions:
  • Forward the necessary ports (port forwarding). Find out the ports required by the application and forward these ports to the IP address of the relevant device in your NAT device.
  • Enable UPnP (if your NAT device supports it). UPnP allows applications to automatically perform port forwarding.
  • Use DMZ (Demilitarized Zone) (as a last resort). DMZ places a device completely outside the firewall. This increases the security risk, so it should be used with caution.

3. Double NAT Problem:

• Problem: When multiple NAT devices are used (e.g., modem and router), internet connection problems or application incompatibility problems may occur.
• Reasons:
  • Conflicts between two NAT devices.
  • Port forwarding issues.
• Solutions:
  • Put one NAT device into bridge mode. This disables the NAT function of the device and allows it to function only as a modem.
  • Forward the ports correctly. If you are using two NAT devices, you may need to forward the ports on both devices.

4. Security Issues:

• Problem: While NAT protects your network from external attacks, incorrect configurations or vulnerabilities can increase security risk.
• Reasons:
  • Leaving unnecessary ports open.
  • Weak passwords.
  • Outdated software.
• Solutions:
  • Only open the necessary ports.
  • Use strong passwords.
  • Keep your NAT device's software up to date.
  • Use a firewall.

Example: Online Game Problem and Solution

A player is experiencing connection problems while playing an online game. The game cannot connect to the server or the connection is constantly dropping due to NAT.

1. Find out the ports required by the game (e.g., TCP 27015-27030, UDP 27000-27015).
2. Forward these ports to the IP address of the player's computer on your NAT device (e.g., 192.168.1.10).
3. Enable UPnP (if possible).
4. Make sure the firewall on the player's computer allows the game.

Real-Life Examples and Case Studies

1. Small Office Network:

In a small office, there are 10 computers. Each of these computers needs to access the internet. However, the office only has one public IP address. NAT is used to solve this problem. The router uses the NAT function to convert the private IP addresses of the 10 computers into a single public IP address. This allows all computers to access the internet at the same time.

Case Study:

An accounting office has started using new cloud-based accounting software. However, it has been noticed that some features of the software are not working. Upon investigation, it was determined that the software communicates over specific ports and that these ports are being blocked by NAT. As a solution, the necessary ports were forwarded on the router, and the problem was resolved.

2. Home Network:

There are multiple devices (computers, phones, tablets, smart TVs, etc.) in a home. Each of these devices needs to access the internet. The router uses the NAT function to convert the private IP addresses of these devices into a single public IP address. Additionally, port forwarding allows external access to specific devices (e.g., security camera).

Case Study:

A family wants to access their home security cameras from outside. However, the IP addresses of the cameras are private IP addresses and cannot be accessed directly over the internet. As a solution, the ports used by the cameras were forwarded on the router, and the family was able to access the cameras over the internet.

3. Game Server:

A person wants to run a game server at home. However, the IP address of the server is a private IP address and cannot be accessed directly over the internet. NAT is used to solve this problem. The ports used by the server are forwarded on the router, and the server can be accessed over the internet.

Case Study:

A student has set up their own server for a popular online game. However, no one can connect to the server from outside. Upon investigation, it was determined that the ports used by the server were being blocked by NAT. As a solution, the necessary ports were forwarded on the router, and players were able to connect to the server.

4. VPN Connection:

A company employee wants to connect to the company network from home via VPN (Virtual Private Network). However, NAT can block the VPN connection. In this case, NAT traversal techniques (e.g., STUN, TURN) or port forwarding can be used to establish the VPN connection.

Case Study:

A company employee is experiencing problems connecting to the company network from home via VPN. Upon investigation, it was determined that the employee's router's NAT was blocking the VPN connection. As a solution, the necessary ports for the VPN protocol (e.g., PPTP, L2TP/IPsec) were forwarded on the router, and the employee was able to connect to the company network without any problems.

These examples and case studies demonstrate how NAT is used in different scenarios and how to solve problems that may arise.

The Future of NAT and its Relationship with IPv6

NAT (Network Address Translation) is a technology developed to alleviate the problem of IPv4 address scarcity. However, with the widespread adoption of IPv6, the future and importance of NAT are being discussed.

Advantages of IPv6:

• Much More IP Addresses: IPv6 provides 2¹²⁸ IP addresses. This is much more than the number of addresses provided by IPv4 (2³²). With IPv6, each device can have a unique public IP address.
• Simplified Network Configuration: IPv6 simplifies network configuration thanks to features such as stateless address autoconfiguration (SLAAC).
• Enhanced Security: IPv6 supports security protocols such as IPsec (Internet Protocol Security).

NAT and IPv6 Relationship:

Because IPv6 provides a large number of IP addresses, the need for NAT is decreasing. Since each device can have a unique public IP address with IPv6, there is no need for private IP addresses and NAT. However, the widespread adoption of IPv6 is taking time, and NAT still retains its importance during the transition periods when IPv4 and IPv6 are used together.

NAT64 and NAT46:

Technologies such as NAT64 and NAT46 have been developed to enable IPv4 and IPv6 networks to work together. NAT64 translates requests from the IPv6 network to the IPv4 network, while NAT46 translates requests from the IPv4 network to the IPv6 network. These technologies play an important role in the transition to IPv6.

The Future of NAT:

Although the need for NAT will decrease with the widespread adoption of IPv6, NAT will not disappear completely. NAT may still be useful in some scenarios:

• Security: NAT can protect devices on the local network from external attacks by hiding their IP addresses.
• Network Management: NAT can simplify IP address management in network topology changes.
• IPv4 Compatibility: NAT may be required to communicate with IPv4 networks.

Conclusion:

IPv6 has reduced the need for NAT by solving the IP address scarcity problem. However, NAT still plays an important role as the transition to IPv6 continues. In the future, the use of NAT will decrease, but it will still continue to be useful in certain scenarios.