Fixing 403 Error with Azure Traffic Manager and gRPC Endpoint

Question

How can I resolve a 403 error when using Azure Traffic Manager with a gRPC endpoint, while the connection works fine when directly using the container app?

PS - Based on common issues that we have seen from customers and other sources; we are posting these questions to help the Azure community.

Answer 1

The 403 error occurs due to a misconfiguration in the Azure Traffic Manager setup. Azure Traffic Manager is a DNS-based load balancer that directs traffic to your services. When using Traffic Manager with a gRPC endpoint, you must ensure that the Traffic Manager endpoint uses the default domain of the container app and not the custom domain.

To resolve this issue:

1. Configure the CNAME record for your gRPC service domain (e.g., grpc.contoso.co) to point to the Traffic Manager domain (e.g., grpc.trafficmanager.net).
2. Set up a TXT record for the container app's custom domain validation.
3. Ensure that the Traffic Manager endpoint is configured with the default domain of the container app, not the custom domain.

By following these steps, you should be able to eliminate the 403 error and successfully use Traffic Manager with your gRPC endpoint.

References:

• Azure Traffic Manager Overview
• Configure Traffic Manager with Endpoints
• Custom Domain and SSL in Azure App Service
• Map domains with Traffic Manager

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