An ultimate guide to port forwarding

An ultimate guide to port forwarding

In order to comprehend port forwarding, you need to comprehend what a TCP/IP port is, and how ports and IP addresses are used together. A TCP port classifies an application or service on an appliance in a TCP/IP network. Every device must have an IP address on a TCP/IP network. The IP address identifies the device. Nevertheless, a device can run multiple applications or services. The port identifies the application or service running on the machine.

Moving on to Port Forwarding…

The router uses Network Address Translation (NAT) which allows internal devices to share a single external IP4 Address. The IP addresses, which are on the internal network, are private addresses. Moreover, these are not routable on the Internet. External computers or devices can only see the public IP address that is assigned to the NAT router interface. The NAT router maps an internal IP address as well as an internal port to the external IP address and external port correspondingly. The external devices send packets to the external IP address and port respectively. The NAT router maps these packets and re-transmits them on the internal network to the internal IP address and internal port.

The ports used by NAT are usually randomly assigned when the session is initiated from the internal network. Do you want to host a website on your internal network? And this website needs to be accessible to external clients? Then you need to use a standard port (port 80 for http) as the external client expects the same. For this, you statically map the external IP address and port 80 to the internal IP address of the webserver and port 80 respectively. This is port forwarding. It enables external devices to access to computer services on private networks. Most online gaming applications require you to configure port forwarding on your home router.

Enabling Port forwarding and Checking Open Ports

Before you setup port forwarding, you need to configure a static IP address for the internal device. This step is substantial because the forwarding will be set in order to send packets to a specific internal IP address. Depending on your application, you might need a list of ports that should be available from the external network i.e. Internet, and forwarded to the internal network. Irrespective of how you configure it, as it varies by device, what you are fundamentally doing is creating a mapping table that maps an external address and port to an internal address and port. Once you have forwarded the ports, you might want to check that they are really opening using an open port checker.

Connecting to a Forwarded Port

In order to connect to the forwarded port from the Internet, it is essential to know the router’s external IP address and the port number that has been forwarded. Nevertheless, using an IP address in the place of a domain name is not very suitable. Furthermore, the external IP address can change as most ISPs assign these addresses using DHCP. So, when using port forwarding, consider using Dynamic DNS.


Port forwarding is configured on home routers. And it is essential because home routers use NAT which separates the home network from the Internet. For any port forwarding services, reach out to us and we will be there to help you!

Just call us on 1300 016 017.

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