Rewrite hostname - App Gateway

Artem Pankratov 0

Hello,

I there a way to rewrite hostname in Azure Application Gateway? I need a way to send requests to another host based on headers.

Thank you in advance,
Artem

Dillon Silzer 60,716 Reputation points Volunteer Moderator

2024-02-18T22:07:51.0733333+00:00

Hi Artem,

You will want to use Rewrite URL with Azure Application Gateway:

Rewrite URL with Azure Application Gateway - Azure portal

https://learn.microsoft.com/en-us/azure/application-gateway/rewrite-url-portal

As demonstrated in the example below:

Cited from https://learn.microsoft.com/en-us/azure/application-gateway/rewrite-http-headers-url#url-path-and-query-string

If this is helpful please accept answer.
Artem Pankratov 0 Reputation points

2024-02-18T22:32:55.6933333+00:00

Hi Dillon,

Thank you for your reply. I did try it, but unfortunately AppGateway seems to support the path rewrite, not the host. For example, I've added the google redirect, but instead it requests http://<my-api-gateway-domain>/https://google.com instead of the google :(

I'd be happy to hear that I've missed something.
ihsan özlü 0 Reputation points

2025-03-19T10:03:36.66+00:00

I've achieved this at Azure Front Door adding a rule set with rewritten URL path and overriding the route.

Please check below ;
https://stackoverflow.com/a/79519797/20731789

1 answer

KapilAnanth 49,851 Reputation points Moderator

2024-02-20T15:44:30.08+00:00
@Artem Pankratov ,

Welcome to the Microsoft Q&A Platform. Thank you for reaching out & I hope you are doing well.

It is not feasible to rewrite the FQDN using Rewrite Rules

While you may change the "Host" header to point to a different FQDN, the requests will still go the Backend Pool which you have configured in your Routing Rule.

This is exactly what is happening in the example references

Instead, you should consider "Redirection",

In your case, it should be "Redirect to external site"

See how to : https://learn.microsoft.com/en-us/azure/application-gateway/redirect-external-site-powershell

Currently, I am afraid this does not support "conditional redirection" where you can achieve this behavior with an If condition.

If the parameters you use for the If condition are in the URL path, you can use a combination of "path-based routing rules" + "Redirect to external site".

Hope this clarifies.

Cheers,

Kapil
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Anonymous

2024-10-11T01:06:12.4566667+00:00

Hi Kapil/MS support, I am trying to achieve the same : Capture a URL 'api.company.com/api?originalQuery' and redirect to 'sitex.company.com/api?originalQuery' based on the query string. SiteX will not necessarily be hosted on the same Backend Pool (and may be an external site).
The official response from Feb 2024 was very clear - "It is not feasible to rewrite the FQDN using Rewrite Rules" - but I want to test if this is still true?
We are migrating from on-prem IIS using 'URL Rewrite 2' to Azure Application Gateway, and want to replicate the rewrite process currently in place. We cannot send a 302 redirect back to the client - we need to process the request and return a 200 (our api consumers are not always sophisticated enough to handle 302 redirection responses.

Thanks, Barnaby

KapilAnanth 49,851 Reputation points Moderator

2024-10-11T06:25:37.4233333+00:00

Hi Barnaby Arnott ,

The behavior is still same and I am afraid this won't change.

The recommendation would be to use "Redirection" only in case of FQDN changes

Cheers,

Kapil
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