APIM configured in External VNet - connection request times out to open.azure.com

Question

We have an APIM set up in an External VNET with the backend web service url (openai.azure.com) configured along with the hostname. We are using OpenAPI spec to test out the endpoints of the backend, but it always ends in a time out error. The backend service has the APIM subnet in the allowed list.
We have the NSG rules for the APIM VNet set from the recommended list:
https://learn.microsoft.com/en-us/azure/api-management/api-management-using-with-vnet?tabs=stv2

Inbound on 443 from the internet was blocked, but the connection should have worked via the VPN which is allowed, but that fails too.

Unsure what else is missing from a networking perspective. Any advice is appreciated!

Answer 1

Thanks for posting your question in the Microsoft Q&A forum.

Ensure that the APIM subnet is correctly configured in the External VNET mode. This mode allows APIM to access the internet directly for backend connectivity. if you have any UDRs applied to the APIM subnet, make sure they're not interfering with the traffic to openai.azure.com.

Verify that APIM can resolve the openai.azure.com hostname. You might need to configure custom DNS servers if you're using Azure Private DNS zones.

Double-check that the Azure OpenAI service is correctly configured to allow access from the APIM subnet IP range.

Ensure that the Azure OpenAI service is operational and not experiencing any outages.

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