Unable to connect Azure AI Foundry to Azure AI Search knowledge base (403 error / DNS resolution issue)

Hi Swapnil Wani (Tata Consultancy Services Limited),

Thanks for sharing the issue. This kind of connection problem usually comes from configuration or network settings rather than a product issue.

From your error, it looks like Azure AI Foundry is not able to properly reach your Azure AI Search service.

Here are a few things you can check:

First, please confirm that the endpoint you used in the connection is correct. The search service endpoint should look like your service name followed by search windows net. Even a small mismatch can cause connection failure.

Second, check the network settings of your Azure AI Search service. If your search service is restricted to selected networks or private access, Foundry may not be able to reach it. In those cases, the request can be blocked or fail during connection. [docs.azure.cn]

Also, if you are using private endpoint or custom DNS, there is a chance that the service name is resolving to a private IP that Foundry cannot access. This usually causes errors like DNS failure or connection timeout.

Third, please verify the permissions. If you are using managed identity or Entra ID authentication, make sure the required roles are assigned to the Foundry project identity. Common roles needed include access to read the search index and access to the search service. [learn.microsoft.com]

Fourth, check that the connection between Foundry and the search service is correctly created inside the project. The connection should reference the correct search resource and index name, otherwise it will not work.

From what we have seen in similar cases, when connection works in one setup but not in another, it usually comes down to one of these points endpoint mismatch network restrictions DNS or private endpoint setup missing permissions

In short, your next step should be to confirm network access and endpoint configuration, since your error looks like the service is not reachable rather than authentication failing.

If possible, try testing once with public access enabled temporarily to see if the connection works. That can help confirm if the issue is network related.

Thankyou!

Hi @Swapnil Wani (Tata Consultancy Services Limited)

We haven’t heard from you on the last response and was just checking back to see if you have a resolution yet. In case if you have any resolution please do share that same with the community as it can be helpful to others. Otherwise, will respond with more details and we will try to help.

Thank you!

Hi Anshika Varshney, SRILAKSHMI C
Thanks for the suggestions, but this didn’t resolve the issue.

• All required roles are already assigned
• “Allow Azure trusted services” is enabled
• Managed Identity is enabled
• Search Service is restricted to selected IP networks

It still fails, so this looks like a network access issue.

Can you confirm if Azure AI Foundry is supported under “trusted services” for Azure AI Search, or what needs to be allowed for connectivity in this setup?

Hi Swapnil - Is this issue got resolved? I am also facing the same issue. Faundry unabel to connect MCP Servers Details: Name or service not known.

Hey KUMAR, ASHISH

Issue here is allowing public Ip from network setting with managed VNET or own VNET.

Customer facing issue 403 even after following private endpoint connection, communication for AI search is restricted through private endpoints only.

Ref - https://learn.microsoft.com/en-us/azure/foundry/how-to/configure-private-link

Managed VNET setup (Deployable through templates) might help here but we are facing issues with customer subscription restriction (Key based auth disabled and other MS internal policies) and issue with template deployment itself.

We have shared the context to product group for the same.

Please create separate issue if it is not helping you.

Thank you.