[DLR] DLR frames are forwarded on both Ethernet ports before device's MAC address is available (certification issue)

DLR frames are forwarded on both Ethernet ports before device's MAC address is available.
In that case, the MAC address that is added into the sign on frame (sent by the DLR supervisor) is wrong (00-00-00-00-00-00).
The device should rather wait for a valid MAC address and then start forwarding DLR frames.

Note: This issue only shows up in case the MAC address is set by the application on startup and the address is not set before the ethernet link is established.