How To Fix CloudFront 421 Error?

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The cloud front 421 error is a generalised error with the HTTP protocol which means that the HTTP is misdirected. This means that the server you were trying to reach did not get your request, and your request was redirected to a different server. You will therefore get a different response than you were expecting.

There are many reasons that can cause the Cloudfront 421 header, and these can range from the problem with SSL certificates to your network to the server. This is why there is a need to understand all the facets of this error code.

How to get rid of the Cloudfront 421 error?

Fix 1: An issue with the SSL certificates

When you use a single SSL certificate for multiple domains, you can face this error code with many platforms online.

This happens because the browser that you are using will reuse the connection that was being used on the previous domain. However, the server that you are requesting services wrong would not be able to handle the request because the names of the host do not match anymore.

In this case, you need to check your SSL certificates and make sure that you are using different SSL certificates whenever you use a different domain.

There are tools like SSL Labs available that can check your SSL certificate status for you.

Fix 2: Make sure that your SNI is configured properly

The full form of SNI is Server Name Indication. This is a feature that makes sure that a single IP address can host multiple websites.

It needs to be configured properly because if it is not then this can cause error codes like 421. You can check your SNI configuration on the CloudFront console. This can also club with the SSL certificate issue that we have discussed in the point above when the browser tries to reuse the connection from the previous domain.

You can solve this problem by making sure that the SNI configuration is correct. Here are the steps to find it.

  • Launch the CloudFront console.
  • Find the name of your distribution and click on it.
  • Now click on the advanced settings.
  • Navigate down to the Server Name Indication(SNI) section.
  • You will see a checkbox next to the SNI-enabled option. Make sure that it is checked.
  • You will now see an option for the SNI domains. Enter the list of the domains here that you want to use with the SNI distribution.

After you have completed this step, you can relaunch and see if this resolves your error code 421.

Fix 3: Check your network

You need to make sure that you are using an impeccable network connection with reliable speed. If the network connection is not stable, then the connection between the client and the CloudFront server will not be able to establish and this will cause the error code 421.

To check the speed of your network you can Google Internet speed meter. Run a test for your network connection.

I doubt that the connection speed is low. Then you can talk to your Internet service provider and ask them to help you with the issue. The Internet service provider will tell you why you’re not enjoying a good signal strength. Maybe it is an issue with your Internet plan that you need to switch, or there is an internal matter that needs to be solved from the side of the network server that will be taken care of by the Internet service provider.

Fix 4: Switch to a different web browser

The web browser that you’re using can run into compatibility issues with the server that you’re requesting.

This can cause the error code 421, which is a generalized HTTP protocol error. 

In this case, you need to switch to a different web browser. This might not solve the issue with the web browser permanently, but if you are in a pinch and need to reach the server immediately, then you can try to use a different web browser.

Fix 5: Disable ad blockers on your web browser

There are many issues on the web browser that are caused solely because of the ad blockers that people use.

The websites that depend on ad revenue do not allow users to use ad blockers while surfing their websites. This gets into a conflict with the web browser and the server. 

If you are in the habit of using her ad blocker on your server, then make sure that you do not do this again and turn off the ad blocker.

After turning off the ad blocker, relaunched the web browser and see if this solves your issue with the platform.

Fix 6: Clear the cookies and cache on your web browser

The web browser stores a lot of information in the form of temporary files like cookies and cache.

This helps when you are regularly using some platforms and you have to re-enter the same information again and again. The data stored in the temporary files is entered automatically and you do not have to go through the tedious process of re-entering the same information.

However, these files also store the data that is corrupt and if it is not cleaned for a long time, it also hogs the working memory of your web browser.

To make sure this does not happen to you, you can clear the cookies and cache on your web browser and relaunch the browser. Now check if you are still facing the error code 421.

Fix 7: Contact the support team

If you have tried each and every one of the solutions that we have mentioned on the list above and you are still facing the error code then you need to contact the support team. By contacting the support team you can raise a support request which can be tracked till the issue is resolved.

You will also get personalized assistance from the developers to help you with the exact solution to your issue.

There are also user forums that you can find through a simple Google search where other users will give you advice on how they solved the issue when they faced the same problem as you.

To conclude

The error code 421 on Cloudfront is an HTTP protocol error, which means that you will not be able to reach the server that you have requested.

We have mentioned all the probable solutions for this issue and we hope that we were able to help you get rid of the issue. These solutions included both official Support Solutions and suggestions from user forums. Keep following for more technical advice.

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Falguni Rana is a technology writer who has expertise in software and hardware troubleshooting. She publishes how-to and troubleshooting guides for different apps, websites, games, and consumer hardware products.