Categories of address forms:
In this type the hardware manufacturer gives permanent physical address to every network manufacturer and interface must ensure that each interface has a unique address.
In this type, the address may be set by the client either manually e.g. jumpers or switches on the interface or electronically. The system administrators have to coordinate to avoid the conflict.
In this type the interface automatically gives physical address every time it is powered up. That automatic function must be reliable to save conflicts.
Some programs want to broadcast messages to every stations on the LAN. For this reason shared communication channel can create broadcast efficient in such a way that message is send to all stations.
A special broadcast address is used to check broadcast message, which are received by all stations.