How Port Forwarding Test Is a Necessity For Port Forwarding?

In the below article we will explore what is port forwarding test, why it is important, and related common mistakes set up.

Port Forwarding Test
Port Forwarding Test | Image by Sumanley xulx from Pixabay

Ports in computer networking have similar functions as physical ports on your computer. Just as physical ports on the computer allow it to connect with other devices such as a mouse, keyboard, and ports in networking, it allows the computer to connect with another computer. Also, the use of ports is seen in the same computer when different services communicate with each other using different ports.

The operating system of computers manages them. Whenever services and applications need to communicate with each other, there should be an open port.


Port forwarding is also known as port mapping. It is a technique by which a router is configured to enable computers or other services in private networks to connect with other public or private computers and network devices over the internet outside the local network.

To simplify this explanation, let us take an example. Suppose you have an IP camera connected to a router. There is also a computer which is connected to the same router.

The router assigns the camera and the computer an internal IP address so that you can communicate with each other on a local area network (LAN). Local IP addresses will almost always start with 192 or 10.

The router is connected to a cable modem to provide internet access to the computers on the network. Modems are also assigned an IP address, but they are different from the local IP address. The internet service provider assigns a modem a public IP address.

The public IP address enables the communication between a local network and devices on the internet.

By default, most routers have a firewall enabled so that no outside internet traffic can enter the local network. This is why port forwarding is needed to provide remote access to devices such as IP cameras.

When you use port forwarding, there is a breach in the firewall, which allows internet traffic inside the network but only on the particular port, you forwarded.


Port forwarding serves a protection to the servers from unwanted traffic. They hide such servers and protect the public IP addresses by limiting access to and from a network. They provide extra protection to the networks.

It enables fixing one public IP address by the network administrators to communicate externally while using multiple servers with different ports internal communications. Port forwarding is very useful for setting up game servers and having access to IP security cameras.


While some routers make the port forwarding set-up easy, some make it complex. In either case, human error is possible. So let us discuss some common mistakes you can commit while setting up port forwarding.

The widely committed mistake is ignorance of the fact that you are behind more than one router. Port forwarding won’t work successfully then.

Putting the wrong IP address is also a widely faced problem. Especially if someone is new to port forwarding, it is common to get confused between LAN and WAN and put the IP address of the computer you want to connect to instead of the device’s IP address, which is getting connected.


Different routers have a different levels of firewall security. So you can easily forget to change the firewall settings suited to your port forwarding rule and find blocked servers.

Firewalls also cause a problem in Windows, Linux, and Mac. You may not even realize that when you have installed anti-virus software, you added firewalls in addition to the firewalls offered by your router. This can make port forwarding difficult due to repeated blocking of connections.

Even less protection is a problem. Because corrupted firewalls in Windows can also inhibit the process of port forwarding.

Some routers allow you to have multiple WAN or internet connections. So this can lead to selecting the wrong connection type, which may not be suitable for your port forwarding rule.

Some modem or routers asks you to enter the computer name instead of IP address to set up port forwarding. In such cases, you may commit a mistake by selecting the wrong name from the list because such routers have your computer name listed several times.

Some routers do not check if a particular port is already in a port forwarding rule. So there are chances you might select the same port with different port forwarding rules.

DMZ is enabled. Since it opens all ports, you can’t be sure if it is pointing to the machine for which you need open ports.

Since there are so many problems that can arise while setting up port forwarding, doing a port forwarding test becomes mandatory.


Port forwarding test enables you to check your external IP address and subsequently check for open ports. It is very useful to verify if the port forwarding setup is successful or if your server applications cannot break through the firewall. It can also be used to scan for a range of commonly forwarded ports.

Using the port forwarding test, you can also check for closed or blocked ports by ISP. Usually, residential ISPs block certain ports to protect the devices from viruses and spam. Port 80 and port 25 are the most commonly blocked ports.

Doing port forwarding tests is easy on the internet. Some provide free services, and some provide paid services. Just by writing the IP address and the port number, different ports’ statuses can be obtained.

Port forwarding test can be of two types. They are port scanning or port checking.

Port scanning helps to scan a range of IP addresses, while port checking checks a single IP address or port’s status.

Some of the services also provide the option of choosing the type of scan for the IP addresses. Such advanced scanning helps to get details about the operating system for the remote IP and scan a host, which is firewall enabled.

Leave a Comment

This site uses Akismet to reduce spam. Learn how your comment data is processed.