The most commonly used link layer protocol (OSI Layer2) in computer networks is the Ethernet protocol. In order to communicate, each node has a unique assigned address, called MAC (Media Access Control address) sometimes it is also called an Ethernet address.
It is 48-bit long and typically fixed by the manufacturer (cannot be changed), but in recent years customization of MAC addresses is widely used, RouterOS also allows to set custom MAC address.
Most commonly used MAC format is 6 hexadecimal numbers separated by colons (
RouterOS shows MAC address in a configuration for all Ethernet-like interfaces (Wireless, 60G, VPLS, etc.)
There are three types of addresses:
- Unicast address is sent to all nodes within the collision domain, which typically is Ethernet cable between two nodes or in case of wireless all receivers that can detect wireless signals. Only remote node with matching MAC address will accept the frame (unless the promiscuous mode is enabled)
- One of the special addresses is broadcast address (
FF:FF:FF:FF:FF:FF), a broadcast frame is accepted and forwarded over Layer2 network by all nodes
- Another special address is multicast. Frames with multicast addresses are received by all nodes configured to receive frames with this address.