Ethernet only deals with MAC addresses. It doesn’t involve any routing or packets. It works with Frames.
- Preamble – Start bits
- Destination (6 bytes) – Destination MAC address
- Source (6 bytes) – Source MAC address
- Length/Type (2 bytes) – Length and EtherType
- Payload (1500 bytes) – Data, zero padded
- FCS (4 bytes) -Frame checksum, CRC
The most important part is the EtherType
- 0x800 – an IP header is next
- 0x806 – ARP is on the way
- 0x8035 – RARP is coming
- 0x810 – this has 801.1q VLAN tags
They can all live in the broadcast domain simultaneously.