Error: The Driver Received an Unexpected Pre-Login Response

Issue

Syncs fail intermittently. The following error appears:

Error: The driver received an unexpected pre-login response. Verify the connection properties and check that an instance of SQL Server is running on the host and accepting TCP/IP connections at the port.

Environment

• All database connectors
• Connection method: VPN or SSH tunnel

Resolution

To resolve this issue, do the following:

1. In Fivetran, go to your connector page.
2. Select the Setup tab.
3. Click Edit connection.
4. In the Host field, enter the private IP address of your database host.
5. Click Save & Test.

Alternatively, if you have configured multiple DNS servers, contact our support team and provide all applicable IP addresses.

Cause

This issue occurs when the SSH server attempts to connect to the database host machine, but the DNS server fails to resolve the hostname you provided in the connector setup form to its corresponding IP address. This may happen due to the following reasons:

• You utilize more than one DNS server, but not all of them are configured to route the applicable hostname to its intended IP address.
• The DNS server experienced temporary issues that resulted in overloaded resources or an unstable connection.