# Connect Reverse ETL Source to SFMC

This guide takes you through the steps to connect a Reverse ETL source to the Salesforce Marketing Cloud (SFMC) destination and specify the data mappings correctly.

## Set up connection

{{< warning >}}
**The Reverse ETL feature supports only source-driven pipeline configuration.**

Make sure you have [set up a RETL source]({{< ref "sources/reverse-etl/_index.md" >}}) and connected it to your SFMC destination before following the below steps.
{{< /warning >}}

1. [Confirm the connection settings]({{< ref "destinations/streaming-destinations/sfmc/setup-guide.md#connection-settings" >}}) for your SFMC destination and click **Continue**.
2. In the **Where do you want to sync data to?** section, select the object **Data Extension** from the dropdown.

{{< image src="images/reverse-etl-destinations/sfmc-object.webp" >}}

3. Set the [Sync mode]({{< ref "data-pipelines/reverse-etl/developer-guides/sync-modes.md" >}}) to specify how RudderStack should sync the data to SFMC. Note that RudderStack supports only **Upsert mode** for this integration.
4. In **Choose identifier** section, specify the warehouse column that RudderStack uses to identify your records.
5. Map the other warehouse columns to specific SFMC fields using the **Map fields** setting.

{{< info >}}
RudderStack populates the SFMC fields based on the data extension external key you provide in the [Identify data external key]({{< ref "destinations/streaming-destinations/sfmc/setup-guide.md#identify-call-settings" >}}) dashboard setting.
{{< /info >}}

{{< image src="images/reverse-etl-destinations/sfmc-identifier-map-fields.webp" >}}

## FAQ

#### Why can't I add a Reverse ETL source from the destination page?

The Reverse ETL feature supports only source-driven pipeline configuration. It means that you must configure a Reverse ETL source in RudderStack and then connect it to a new or existing destination. Note that this destination should not be connected to any other source.

See [Reverse ETL FAQ]({{< ref "data-pipelines/reverse-etl/developer-guides/faq.md" >}}) for more information.

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