2 NAT Configuration Explained

1. Understanding NAT (Network Address Translation)

NAT is a method used to modify IP address information in IP packet headers while they are in transit across a traffic routing device. It is primarily used to map multiple private IP addresses to a single public IP address, allowing multiple devices on a local network to access the internet using a single public IP.

Key Concepts

• Source NAT (SNAT): Changes the source IP address of a packet. This is commonly used to allow internal devices to access the internet by translating their private IP addresses to a public IP address.
• Destination NAT (DNAT): Changes the destination IP address of a packet. This is used to forward incoming traffic from the internet to specific devices within a private network.

2. Configuring NAT in MikroTik

a. Source NAT (SNAT)

Source NAT is used to allow devices on a private network to access the internet. The private IP addresses of these devices are translated to a public IP address before the packets are sent out to the internet.

Example Configuration:

In this example, all outgoing traffic from the private network (ether1) is translated to the public IP address of the router, allowing devices on the private network to access the internet.

b. Destination NAT (DNAT)

Destination NAT is used to forward incoming traffic from the internet to specific devices within a private network. This is often used for services like web servers that need to be accessible from the internet.

Example Configuration:

In this example, incoming TCP traffic on port 80 is forwarded to the private IP address 192.168.1.10, allowing a web server on the private network to be accessible from the internet.

3. Practical Examples and Analogies

a. Source NAT (SNAT)

Imagine a large office with many employees who need to access the internet. Instead of giving each employee a unique public IP address, the office uses a router with NAT. The router translates the private IP addresses of the employees to a single public IP address, allowing them all to access the internet through a single connection.

b. Destination NAT (DNAT)

Consider a small business that hosts its own website. The website server is located within the business's private network. To make the website accessible from the internet, the router uses DNAT to forward incoming web traffic (port 80) to the server's private IP address, allowing users on the internet to access the website.

By mastering NAT configuration in MikroTik, you can create a flexible and secure network infrastructure that allows internal devices to access the internet while also making specific services available to external users. This knowledge is essential for anyone aiming to become a MikroTik Certified Routing Engineer.