iPhones have been exposing your unique MAC despite Apple’s promises otherwise — “From the get-go, this feature was useless,” researcher says of feature put into iOS 14::“From the get-go, this feature was useless,” researcher says of feature put into iOS 14.
The way multicast works is that the destination mac address starts with 01 00 5e and then next 3 octets (mac addresses are 6 octets long) are copied from the IP address lower octets. The mac address is always this when building the L2 headers for the packet.
It’s not specified what precisely is provided in the payload of the multicast body. I suspect that the original MAC address is included in something like a Bonjour broadcast, but I wasn’t able to find any documentation that confirms that.