# Amazon IoT Greengrass V2
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## Compatibility with Amazon IoT Greengrass V2 devices
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 Amazon IoT Greengrass V2 support for client devices is backwards-compatible with Amazon IoT Greengrass V1. You can connect FreeRTOS client devices to V2 core devices without changing the application code. To enable client devices to connect to a V2 core device, do the following. 
+  Deploy Greengrass software to the Greengrass core device. See [ Connect client devices to core devices](https://docs.amazonaws.cn//greengrass/v2/developerguide/connect-client-devices.html) to connect a device to Amazon IoT Greengrass V2.
+  To relay messages (including Lambda functions) between client devices, Amazon IoT Core cloud service, and Greengrass components, deploy and configure the [ MQTT bridge component](https://docs.amazonaws.cn//greengrass/v2/developerguide/mqtt-bridge-component.html).
+ Deploy the [ IP detector component](https://docs.amazonaws.cn//greengrass/v2/developerguide/ip-detector-component.html) to automatically detect connectivity information, or manually manage the endpoints.
+ See [ Interact with local Amazon IoT devices](https://docs.amazonaws.cn//greengrass/v2/developerguide/interact-with-local-iot-devices.html) for more information.

For more details, see Amazon documentation about running [Amazon IoT Greengrass V1 applications on Amazon IoT Greengrass V2](https://docs.amazonaws.cn//greengrass/v2/developerguide/migrate-from-v1.html#connect-v1-greengrass-devices).