How to Fix “ERR_TUNNEL_CONNECTION_FAILED” Error

The “ERR_TUNNEL_CONNECTION_FAILED” error comes up when Google Chrome fails to connect to a proxy server. In this article, I’ll show you how to fix this error, how to replicate it, and how you can prevent it from occurring again in the future.

Here’s a screenshot of what the error looks like:

The easiest way to fix this error is to check your VPN connection settings. The best way to demonstrate this is to show you how to replicate the error.

How to Replicate the “ERR_TUNNEL_CONNECTION_FAILED” Error

On a Windows machine, we can replicate the “ERR_TUNNEL_CONNECTION_FAILED” by creating a fake VPN and trying to connect to a website. In the Google Chrome settings, search for “proxy”, and click the result which says “Open your computer’s proxy settings” like this:

This will open the Windows VPN connection settings. Click “Set up” to create a new proxy server:

In the proxy server settings, enter the following details:

1. Proxy server address: 192.0.2.0
2. Port: 8080

Here’s what the settings screen looks like:

The combination of this address and port should create a non-routable proxy server to which it’s impossible to connect. Now when you visit a website, you might get the “ERR_TUNNEL_CONNECTION_FAILED” that we’re looking for.

Why You Might Get a Different Error

After trying the above steps, you might get a different error like “ERR_TIMED_OUT”, instead. This is because the kind of error message you get is highly specific to network conditions, and replicating the exact error can be challenging. If you really want to replicate the error, you’ll have better chances of creating your own (real)proxy server and then changing the SSH key on the server. This way, you’re forcing the proxy server itself to refuse the error, which your Google Chrome browser might interpret differently and cause it to throw the “ERR_TUNNEL_CONNECTION_FAILED” error.

Changing your server’s public key leads to the “Remote Host Identification has Changed” error.

Other Methods To Fix ERR_TUNNEL_CONNECTION_FAILED

Here are some other suggestions that can help you fix the “ERR_TUNNEL_CONNECTION_FAILED” error.

#1. Disable your Firewall or Antivirus (Temporarily)

One of the troubleshooting steps you should try to get rid of this error is to disable your anti-virus or Windows firewall. Of course, this isn’t a permanent measure, but it’ll help you see where the problem lies. The reason this might work is that some firewalls work by intercepting your traffic and routing them through a proxy server, and if that’s misconfigured, then it can throw this error.

It’s not clear what you can do to immediately solve this problem, other than disabling your protection, but that’s not a long-term solution. You might just need to wait for the problem to fix itself, or you could switch to an alternative firewall provider.

#2. Reset Your Network

The next thing to try is to reset your network configuration. This procedure will temporarily disable your network adapter and start it up again. It could fix some lingering connection problems. If this works, it’s by far the easiest way to resolve this error. To do this, simply open the Windows start menu and type “Network Reset”, and in the resulting dialog box, click “Reset now” as shown here:

Wait for the connection to reset, cross your fingers, and hope it works.

#3. Disable Your Proxy Server

Another way to try and isolate the problem is to disable your proxy server entirely. If, after disabling it, you’re still unable to connect to your sites, it means that the “ERR_TUNNEL_CONNECTION_FAILED” is a red herring, and the actual problem lies elsewhere. In the first set of steps where I showed you how to replicate the problem, go to the same system settings dialog box and disable the proxy server by setting the toggle button to “Off”.

If you’re able to connect to your site after disabling the proxy server, then at least we know that the issue lies in the proxy server configuration, and not with a deeper, underlying issue.

#4. Reset Your DNS Cache

The next step is to flush your DNS cache. This is quite easy to do on Windows. Here are the steps.

First, click the start button and type “cmd”. This will open a new command prompt window. For this operation, you might find it necessary to right-click the “Command Prompt” app and click “Run as Administrator” if the following steps don’t work.

In the command prompt, type the following;ipconfig /flushdns

If you have the right permissions, Windows should now flush your DNS cache. Here’s a screenshot:

One reason why flushing the DNS cache can fix the “ERR_TUNNEL_CONNECTION_FAILED” error, is that your DNS cache might contain corrupted entries, or perhaps the IP address that your VPN uses has changed, and it’s not yet reflected in the cache. Windows can also cache the responses from DNS servers, so it’s possible that the issue has been fixed, but you’re not receiving the latest responses.

For a variety of other reasons, including stale gateway endpoints and mismatches in configurations, flushing your DNS entries has a good chance of fixing this error.

#5. Change Your DNS Server

I often use Cloudflare’s DNS servers on my Windows machine in any case, and this is as good a time as any to see if changing your DNS server can fix your “ERR_TUNNEL_CONNECTION_FAILED” error. Here’s how to do it.

First, open the network connections window by right-clicking on the network icon in the system tray. Here, you’ll see a list of all the network connections available on your machine. Chances are that you’re on WiFi like I am, so select the icon through which you’re currently connected to the Internet like this:

Of course, if you’re using a wired connection, then choose that one instead. Right-click it and choose “Properties“.

In the next dialog box, you’ll see a list of items, one of which will be the Internet protocol. In the screenshot below, it’s “Internet Protocol Version 6”. Select that and choose “Properties”, once again:

In the next dialog box, in the second section, choose the option that says “Use the following DNS server addresses” and type the following into the two boxes:1.1.1.1
1.0.0.1

Here’s what it looks like:

Validate your settings, and click “OK”. Then flush your DNS cache once again, just in case. To test if your computer is using Cloudflare’s DNS servers, visit the following website: https://one.one.one.one/help/ .

If you’ve followed the above steps correctly, you should see something like this:

And you’re done! Now try connecting to your VPN once again, and hopefully, this time the problem is solved.

#6. Use A VPN Software (Instead of a Windows Setting)

See if, instead of setting up a VPN through Windows, you can use a VPN software like OpenVPN (which I’m using the write this article). VPN applications like this take care of all the hard work for you, and you don’t need to bother with settings and configurations. This reduces the probability of errors, and you need never deal with the “ERR_TUNNEL_CONNECTION_FAILED” error again.

Conclusion: Many Solutions to the Problem

As you can see, there are many ways to solve the “ERR_TUNNEL_CONNECTION_FAILED” error. It’s hard to pinpoint an exact cause because there are so many failure points. But if you follow the above steps one by one, you’ll eventually hit the right cause, and hopefully, that’ll fix the problem!