ISP Blocking Port Forwarding: How to Know?

Here’s how to know your ISP is blocking port forwarding:

An ISP can only block port forwarding if they control your router, so this is only an issue if they provided the router that you use. 

When that is the case, you can log into the router and look at the port forwarding settings.

If you can’t see those settings, then the safe assumption is that port forwarding is blocked.

So if you want to learn all about how to know exactly if your ISP blocks port forwarding, then you’re in the right place.

Without further ado, let’s get into it!

ISP Blocks Port Forwarding: How to Know? (Do This)

What Is Port Forwarding?

In a nutshell, port forwarding is what allows devices inside different private networks to talk to each other. 

That explanation involves some terminology, so let’s break it down.

First, what is a private network? 

You might have heard the term VPN advertisements, but a VPN is only one type of private network (a virtual private network, to be specific). 

Really, a private network is anything that can’t be accessed from other devices. 

So, your home Wi-Fi is a private network (or at least it should be). 

The network that a website host uses is also private. 

Typically speaking, the actual devices we all use are on private networks (although it’s more complicated with phone networks).

Here’s the thing. 

Your computer is on a private network (probably). 

At the same time, the actual device that runs the website you’re trying to load is also on a private network. 

Since they’re both private, they can’t talk to each other. 

That’s what privacy is all about in this case.

So, how do you actually load a website? 

Port forwarding is the answer. 

Your router works as a middleman. 

The router creates a “mask” for your computer. 

This is a serial number that identifies your device within your own network, but it doesn’t give outside devices direct access to you.

The easiest way to think of this is with an analogy, so think about P.O. boxes.

It’s an address that people can use to send things to you, but it doesn’t tell them where you live. 

With port forwarding, your router is creating a P.O. box for your computer. 

The same thing is happening at the other end of the website. 

Whatever server actually holds the website information has its own router (or some other device to manage port forwarding). 

So, in a way, your computer and the webserver are really communicating via a pair of P.O. boxes. 

They don’t know each other’s real addresses.

This maintains a level of privacy, and I’ll explain why that matters in a minute.

The gist is this. 

If you’re loading a website, hosting a game server for your friends, or using the internet in a general sense, there’s a good chance that port forwarding is involved. 

It allows the various devices to communicate with each other while maintaining privacy.

What Does Blocking Port Forwarding Do?

But, why does all of this matter? 

Why can’t the web server and your computer just communicate directly? 

That’s physically possible, but it’s risky. 

Port forwarding prevents outsiders from having a direct line to your device, and that ultimately makes hacking a lot harder. 

It doesn’t make hacking impossible, but without port forwarding, it takes a lot less effort to access someone’s device.

If you’ve ever hopped on a public Wi-Fi network, you might have seen a notice asking if it’s a private or public network. 

Public networks don’t use port forwarding, so it’s a lot easier for hackers to mess with devices on public networks. 

There are security measures you can take, and that’s why your device asked you in the first place. 

You want to be careful when port forwarding isn’t in place.

The second thing port forwarding does is allow devices on different networks to form a stable connection with each other. 

This makes it easier to maintain communication. 

So, if you’re doing your taxes on the TurboTax website (instead of downloading an app), then you need port forwarding to stay connected and get the work done. 

(Technically, you could do this with a non-private connection, but then your device and TurboTax would be operating at a higher risk.)

So, if port forwarding is disabled, it can make two-way communication with remote devices difficult or even impossible. 

You need port forwarding to stay on a website, host a game server, host your own website, or do any number of other things on the internet.

How Can Your ISP Block Port Forwarding?

Clearly, port forwarding is important, so why would it ever be blocked? 

There are a lot of reasons. 

The most common have to do with security and censorship. 

As an example, there are specific ports that are relegated for specific applications. 

Port 25 is reserved for simple mail transfer protocol. 

If you use an email app, it needs access to port 25.

Some ports are a little more specialized, and there might be good reasons to block them. 

Port 3389 is the remote desktop protocol port. 

If this port is open, other devices can remotely connect to your computer and control it. 

So, internet service providers (ISPs) might block this port by default as a safety precaution.

In countries with heavily restricted internet access, port blocking can prevent users from accessing tools that get around censorship. 

Ultimately, there are a lot of ports with a lot of functions, so the exact motive really depends on the situation.

But, in order to block a port, the person would need direct access to your router. 

If your ISP is blocking a port, it means they can access your router. 

In other words, you have to use a router provided by the ISP in order for them to even have this power. 

If you own your own router, they can’t block your ports.

That said, there is a different technique that ISPs can use. 

They can block all incoming traffic. 

Technically, it’s not the same as blocking port forwarding, but it has the same end result, and they don’t need access to your router for this.

By blocking all incoming traffic, they can make it impossible for you to host your own website, establish secure connection tunnels, or even download information from the internet. 

With sophisticated software, ISPs can allow traffic from pre-approved sources and block everything else.

This is how countries with restrictive internet policies (like China or Iran) control internet activity. Well, it’s one way.

How Do You Know If Your ISP Blocks Port Forwarding?

Finally, we can get back to the original question and answer it in better detail. 

For starters, if your ISP can’t manage your router, you know that they are not blocking port forwarding. 

If they do manage your router, you should still be able to log into the router and take care of some management yourself.

To do this, you need to directly access your router, and this video can help with that. 

Once logged into your router, you can see the settings. 

You should be able to manage port forwarding from there.

It’s possible that port forwarding management is blocked or not available in this management software. 

If that’s the case, you can safely assume that it is being blocked, or at least regulated.

If you want to change that, you’ll have to talk to your ISP and hope that they unblock port forwarding. 

Or, you can replace the ISP router with one of your own and manage it as you see fit.


  • Theresa McDonough

    Tech entrepreneur and founder of Tech Medic, who has become a prominent advocate for the Right to Repair movement. She has testified before the US Federal Trade Commission and been featured on CBS Sunday Morning, helping influence change within the tech industry.

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