Table of Content
Table of Content
What is a NAT router
A NAT (Network Address Translation) router is a networking device (Eg: your home WiFi router) that performs Network Address Translation, enabling multiple devices on a private local area network (LAN) to share a single public IP address when connecting to the internet.
It acts as the gateway for all traffic between the internal network and the outside world.
Your NAT router or the WiFi router also has a firewall service running that blocks, by default, all traffic from the internet from reaching your devices in your private network.
In office networks, the NAT service is typically performed by a gateway router or a dedicated firewall device that acts as a gateway between a private internal network and a public external network (like the internet). It dynamically translates the private IP addresses of devices within the local network to a single public IP address (or a pool of public IPs) when those devices communicate outside, and vice-versa for return traffic.
How a NAT router works:
A NAT router generally works by routing traffic from devices in the private network to the devices or systems in the public internet. This is typically done by mapping or translating the internal private IP address and port number to an external public IP address and port.
Private IP Addresses:
Devices within your home network (your laptop, smartphone, smart TV, IoT devices) are assigned private IP addresses (e.g., 192.168.1.x, 10.0.0.x). These addresses are not routable on the public internet, meaning they are only unique within your local network.
Public IP Address:
Your router has a single public IP address assigned by your Internet Service Provider (ISP). This is your network’s “identity” on the internet.
Translation Process:
When a device in your private network wants to access the internet (e.g., fetch a webpage), it sends a request to the NAT router. The router intercepts this request, changes the source IP address from the device’s private IP to its own public IP address, and also assigns a unique port number to that specific connection. It then sends the request to the internet.
Tracking Connections:
The NAT router maintains a “NAT table” that maps the outgoing public IP address and port number back to the original private IP address and port number of the internal device.
Returning Traffic:
When the response from the internet arrives at the router’s public IP address and the associated port, the router consults its NAT table. It then translates the destination IP address back to the correct private IP address of the original requesting device and forwards the data to that device.
Why NAT is used:
IP Address Conservation: The most significant reason for NAT is to combat the exhaustion of public IPv4 addresses (which are a scare resource, for technical reasons). With a limited number of public IPv4 addresses available, NAT allows countless devices to connect to the internet using a much smaller pool of public IPs. A NAT router performs many-to-one mapping between many private IP addresses and a single public IP address.
Security (by obscurity): By hiding the private IP addresses of internal devices, NAT adds a layer of security. External entities on the internet cannot directly “see” or initiate connections to individual devices within your private network.
Why it is difficult to remote access an IoT device behind a NAT router or Firewall:
The very mechanism that makes NAT useful for IP conservation and basic security is what makes remote access to devices behind it challenging.
Here’s why:
No Direct Inbound Connection:
When an external device (e.g., your smartphone trying to connect to your IoT device from outside your home network) sends a request to your router’s public IP address, the router doesn’t automatically know which internal device (like your smart thermostat or camera) that request is intended for.
The NAT table only records connections that originated from the internal network. If the internal IoT device hasn’t initiated an outbound connection to the external remote access service, there’s no entry in the NAT table for the router to use to forward the incoming request.
This is like trying to call someone in an apartment building when you only know the building’s address and not the specific apartment number. Firewall Functionality:
Most NAT routers also include basic firewall functionality. This firewall, by default, is configured to block unsolicited incoming connections from the internet to your private network. This is a security measure to prevent unauthorized access.
For a remote access attempt to succeed, this firewall needs to be explicitly configured to allow the connection.
Dynamic Public IP Addresses:
Many ISPs assign dynamic public IP addresses to residential and small business routers. This means your router’s public IP address can change periodically.
If you’re trying to connect to your IoT device using its public IP, and that IP changes, your connection will fail. You’d need a Dynamic DNS (DDNS) service to constantly update a hostname with your router’s current public IP.
Common (but problematic or complex) workarounds for NAT challenges:
These are workarounds and not solutions for overcoming NAT challenges.
Port Forwarding:
This involves manually configuring your router to direct incoming traffic on a specific public port to a specific private IP address and port of your IoT device.
Challenge: Requires manual configuration for each device, can be complex for non-technical users, and significantly reduces security by exposing a specific port of your internal device directly to the internet, making it vulnerable to scanning and attacks. Also problematic with dynamic IPs without DDNS.
Demilitarized Zone (DMZ):
You can assign a device to the DMZ, outside the scope of the firewall, which essentially exposes all of its ports directly to the internet.
Challenge: This is a major security risk as it bypasses the firewall entirely for that device. Rarely recommended for IoT devices.
VPN (Virtual Private Network):
You can set up a VPN server within your private network or on a device inside the network. This creates a secure tunnel, making your external device appear as if it’s on the local network.
Challenge: Requires technical expertise to set up and manage, and the VPN server itself still needs to be accessible from outside (often requiring port forwarding).
UPnP (Universal Plug and Play):
Some devices use UPnP to automatically request port forwarding from the router.
Challenge: While convenient, UPnP is often considered a security risk as it can allow devices to open ports without explicit user approval.
Modern Solution (SocketXP)
Solutions like SocketXP overcome these NAT and firewall limitations by establishing outbound-initiated connections (a.k.a reverse proxy connections) from a device in the private network to a cloud-based service in the internet.
Since the IoT device initiates the connection, it appears as legitimate outbound traffic to the NAT router and firewall.
The cloud service then acts as a secure intermediary, creating a secure SSL/TLS based VPN-like encrypted tunnel that allows remote access to the IoT device without requiring any complex port forwarding or exposing the device directly to the internet by pin-holing firewalls.
This is often referred to as a reverse proxy tunnel or secure tunnel.
SocketXP IoT Remote Access Solution leverages SSL/TLS based secure reverse proxy tunnels to remotely connect to IoT devices, Raspberry Pis, Nvidia Jetsons or any embedded Linux edge devices behind NAT router and Firewall.