How does Network Address Translator work?
What Is NAT?
NAT, which stands for network address translation, is a technique that allows multiple private addresses in a local network to be mapped to a single public IP address before data is sent to the internet. This method is used by organizations and most home routers to enable several devices to share one IP address. If you're accessing the internet from home, your cable modem or DSL router is probably using NAT for your network.
Network Address Translation (NAT) operates by converting private IP addresses within a local network into a single public IP address for internet communication. This process enables multiple devices on a private network to access the internet using just one public IP address, thereby conserving IP addresses and providing an additional security layer by concealing internal network details from external entities. The translation typically occurs on a router functioning as a gateway between the private network and the public internet, where it modifies the source IP address of outgoing packets and reverses the process for incoming traffic.
How does Network Address Translator work?
How Does NAT Work?
Consider a scenario where a laptop is connected to a home network utilizing NAT. This network is ultimately linked to a router that connects to the internet. Imagine someone using this laptop to search for directions to their favorite restaurant.
The laptop operates under NAT, sending the request in an IP packet to the router, which then forwards the request to the internet and the search service being used. Before the request exits the home network, the router converts the internal IP address from a private local IP address to a public IP address. Essentially, your router translates the private address into one that is internet-compatible and then back again. This demonstrates that your cable modem or DSL router has an automated translation function within it.
If the packet retains a private address, the receiving server will be unable to determine where to send the response. This is because a private IP address cannot be routed on the internet. Should your router attempt this, all internet routers are programmed to automatically discard private IP addresses. Fortunately, all routers available today for home and small office use can efficiently translate between private IP addresses and publicly-routed IP addresses.
Key Points about NAT:
Function:
NAT serves as a translator, converting private IP addresses used within a local network into a public IP address that is accessible on the internet.
Implementation:
Typically implemented on a router, NAT intercepts data packets and modifies the source IP address before forwarding them to the internet.
Security Benefit:
By concealing the internal network behind a single public IP, NAT enhances protection against unauthorized internet access.
Address Conservation:
NAT enables multiple devices to share a single public IP address, which is essential due to the limited availability of IPv4 addresses.
NAT Types
There are three distinct types of NATs utilized by individuals and organizations for various purposes, yet they all function as NATs.
Static NAT
This type of NAT consistently maps a local address to the same public address, ensuring a stable public IP address is associated with the router or NAT device.
Dynamic NAT
Dynamic NAT selects from a pool of public IP addresses rather than using the same one each time. Consequently, the router or NAT device receives a different public address whenever it translates a local address.
PAT
PAT, or port address translation, is a form of dynamic NAT. It associates multiple local IP addresses with a single public address. Organizations often employ PAT to consolidate all employee activity under one IP address, typically managed by a network administrator.
Why Use NAT?
NAT is a simple process, with most commercial routing equipment automatically implementing it or enabling it with a single click. Let's delve deeper into NAT’s role in IP conservation and its limited security functions.
IP Conservation
IP addresses uniquely identify each device connected to the internet. IPv4, the current version, uses 32-bit numbered IP addresses, offering 4 billion possible addresses—considered ample when introduced in the 1970s.
However, the internet's growth has been exponential. While not all 7 billion people globally access the internet frequently, those who do often own multiple connected devices such as phones, desktops, laptops, tablets, TVs, and even smart appliances.
As a result, the number of internet-connected devices exceeds the available IP addresses. NAT facilitates the consolidation of multiple private IP addresses into a single public IP address, thereby conserving public IP addresses despite the proliferation of private ones.
IPv6: More Addresses and Routing Efficiency
IPv6 was officially launched on June 6, 2012, after decades of development, primarily to address the demand for more IP addresses, a demand traditional NAT struggled to meet. IPv6 employs 128-bit numbered IP addresses, providing exponentially more potential IP addresses than IPv4. While the transition to IPv6 will take years, NAT for IPv4 addresses remains prevalent. Importantly, IPv6 not only offers a significantly larger address space but also enhances routing efficiency, reducing the processing burden on routers compared to IPv4.
Understanding the Practical Functionality of NAT:
Outgoing Traffic:
When a device within the local network transmits data to an external server, the router, functioning as a NAT, substitutes the device's private IP address with its own public IP address before forwarding the packet to the internet.
Incoming Traffic:
Upon receiving a response from the internet, the router utilizes the information stored in its translation table to accurately identify the appropriate device on the local network and deliver the data to it, once again replacing the public IP address with the original private IP address.
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