Hello @EnterpriseArchitect ,
From your question, it looks like you are trying to enable diagnostic logs for Azure application gateway and were able to successfully enable it for your production gateway but are unable to do the same for Dev and testing subscriptions.
You have an event hub in your production subscription and you are trying to add the same event hub when enabling diagnostics for Dev and testing application gateways. Is that correct?
If that is correct, the Event Hubs namespace does not have to be in the same subscription as the subscription that's emitting logs, as long as you have appropriate RBAC access to both subscriptions and both subscriptions are in the same AAD tenant. So I would recommend you to check your RBAC access for all 3 subscriptions and also check if they are in the same AAD tenant.
For more details, please refer the below articles:
https://learn.microsoft.com/en-us/azure/application-gateway/application-gateway-diagnostics#enable-logging-through-the-azure-portal
https://learn.microsoft.com/en-us/azure/azure-monitor/platform/diagnostic-settings#event-hub
Hope this helps!
Kindly let us know if the above helps or you need further assistance on this issue.
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