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Entry type: FAQ Entry ID: 109474556, Entry date: 10/09/2017
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Why is the WLAN client connected to the Access Point but the PROFINET connection to the distributed IO is not established and what does the MAC mode do on the WLAN client?

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With a SCALANCE W that is parameterized as WLAN client you can set 4 different MAC modes. The MAC mode decides how the WLAN client behaves with respect to the Access Point and whether the PROFINET connection to the distributed IO can be established.

In a WLAN it holds for the Access Point that each client has one single MAC address. With a SCALANCE W the WLAN client should only function as a gateway into the WLAN for a controller or PROFINET IO devices. For this to function the MAC mode must be set accordingly. In the following we describe the MAC modes.

Automatic
The WLAN client automatically takes the source MAC address of the first message which it receives via the Ethernet interface. Until a first message is received, the MAC address of the Ethernet interface of the WLAN client is used. The WLAN client communicates with the Access Point with this MAC address. The MAC mode "Automatic" only functions with a node after the WLAN client. Only this node can communicate by Layer 2 via the WLAN segment.

Manual
The WLAN client takes the configured MAC address. If you use the MAC mode "Manual", you must configure the MAC address that is to be used. This MAC mode is useful when multiple nodes are after the WLAN client and only exactly one of them is to communicate by Layer 2 via the WLAN segment.

Own
The WLAN client uses the MAC address of the Ethernet interface for the WLAN interface. Only the WLAN client can communicate by Layer 2 via the WLAN segment.

Layer 2 tunnel
The WLAN client uses the MAC address of the Ethernet interface for the WLAN interface. In addition, the Access Point is informed about the MAC addresses connected to the Ethernet interface of the WLAN client. Up to 8 MAC addresses can be logged on to the Access Point, in other words up to 8 nodes after the WLAN client can communicate via the WLAN segment. In operation, WLAN Client and Access Point pack up each message with their own source and destination MAC address or they unpack the original message again to forward it.

The message sent by the IO controller is packed by the Access Point in a message with its own MAC address and the MAC address of the WLAN client. The WLAN client unpacks the original message. In the opposite direction the messages are packed in exactly the same way.
The Layer 2 tunnel must be used if there is more than one PROFINET node. The WLAN client is also included here.

Note
The Layer 2 tunnel can only be used with SCALANCE W Access Points and not with other Access Points from third-party manufacturers.



Fig. 1

Further Information
Detailed configuration instructions are available in entry 92649989.


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