A Media Access Control (MAC) address is a hardware identifier assigned to network interfaces such as Ethernet cards and Wi-Fi adapters for communication on a local network. It is hardcoded into the network hardware during manufacturing and is used at the data link layer (Layer 2) of the OSI model. One of the most important features of MAC addresses is that they must be unique. Each MAC address is meant to be globally unique, and manufacturers bear the responsibility of ensuring that no two network interfaces have the same MAC address, though this can be a challenging task to accomplish in practice, especially in virtualized environments. This can be an issue with networking, as duplicate MAC addresses on any network will cause issues. Additionally, many of the bonding modes rely on MAC addresses to load balance traffic.
