When your computer wants to send a packet to some IP address x.x.x.x, then the first check is if the destination address is in the same IP network as the computer itself. Another protocol for example would be IPX. IP is a protocol that is used on a layer above ethernet. How do IP addresses and MAC addresses work together? There are special MAC addresses, one for example is ff:ff:ff:ff:ff:ff, which is the broadcast address and addresses every network adapter in the network. If the addresses match, the packet is processed, otherwise it is discarded. If a network adapter is receiving a packet, it is comparing the packet’s destination MAC address to the adapter’s own MAC address. Packets that are sent on the ethernet are always coming from a MAC address and sent to a MAC address. Network cards each have a unique MAC address. MAC addresses are the low level basics that make your ethernet based network work. SuperUser contributor Werner Henze offers some insight into the function of the MAC address: Where indeed? What is the specific function of the MAC address? The Answer So my question is, where exactly does a MAC address come into play during a packet transfer?

I don’t think it sits there for no reason. So, MAC addresses are not used for packet transfer. With MAC addresses, there is no hierarchy, and thus packet forwarding would not be possible. I understand that IP addresses are hierarchical, so that routers throughout the internet know which direction to forward a packet. SuperUser reader Vishnu Vivek is curious about MAC addresses and their function:

How to find alternate mac address