Azure API Management custom domains - issue with Management API access - 503 error

Question

Hi,

I configured Azure API Management using External VNET integration mode. I configured two custom domains in the APIM:

• One for gateway (traffic goes through the Azure Front Door)
• One for Management API (traffic goes through the Azure Front Door)

I noticed that APIM Developer Portal connects with Management API of APIM underneath. When I use default domain, Developer portal can reach Management API (under xxx.management.azure-api.net) but when I enable custom domain for Management API of APIM, I see that Developer portal is trying to access Management API under custom domain but error 503 is returned.
It looks like there is a problem with accessing Management API of APIM when custom domain is used.
I have certificates in my Key Vault for both domains and they are successfully referenced.

Here is my config:

Do you have any ideas why it does not work? I do not want APIM Developer portal to use default domain of Management API. I plan to use Azure Front Door with APIM as a next step.

Answer 1

@Daniel Krzyczkowski Thanks for reaching out. The issue can be observed due to multiple reasons and I was able to reproduce the issue in the below scenario.

• If you are using a self-signed cert for your custom domain (management endpoint)
• The certificate may have expired
• The custom domain is mapped incorrectly with the IP address

I believe you might have already looked into the Prerequisites and other sections on the document but suggest you to review it again to see if it helps you to verify the configuration again at your end.

To troubleshoot it further we will be ending your APIM instance details so we can review the configuration of APIM at our end to confirm if there is any configuration issue. In case if you are still facing the issue then please respond only to my private comment to share the APIM instance details.