Troubleshooting Connection Issues with Mongo DB using VNET Data Gateway

Hi alfBI , Thank you for reaching out to the Microsoft Community Forum.

From your errors, Fabric is able to reach your MongoDB (the connection arrives at MongoDB), but it is trying to open a TLS/SSL connection, while your MongoDB server is running without SSL enabled. MongoDB therefore closes the connection immediately during the handshake, before any authentication happens.

This is not a firewall, DNS or credential problem. The failure happens at the transport layer, not at the login layer. Fabric’s VNET Data Gateway always uses secure (TLS) connections for MongoDB and does not support plain TCP connections. There is no setting in Fabric to disable SSL.

You must either enable TLS on MongoDB or place MongoDB behind a TLS-terminating proxy. If MongoDB remains non-TLS, Fabric will never be able to connect.

Good question, unfortunately it is not possible to execute this command from the Fabric VNet. Anyway we have checked that the problem comes from the fact that Mongo DB did not have TLS enabled (Fabric requires TLS 1.2)