Hi there,
Is it possible to configure the Ethernet shield without providing the mac address to Ethernet.begin() ?
Or alternatively somehow detect the MAC address of the Ethernet Shield during run time?
I understand than the logic behind this is that there may be more than one Ethernet Shields present and then it is necessary to provide the MAC address in order to assign the IP to the desired shield only, but it seems like an unnecessary burden if there's only one shield present (which is I guess the case most of the times).
No, it isn't possible. The Ethernet shield does not have a hardware supplied mac address, so you need to assign it one.
I was not aware of that.
Does this mean that I can assign any MAC address (instead of the one provided in the sticker under the shield) and still work, as far as it does not conflict with any other MAC address in the local network?
Yes, it does. That's why all the Ethernet library example sketches can use the same address.