Suggest an editImprove this articleRefine the answer for “What fields does an Ethernet frame consist of?”. Your changes go to moderation before they’re published.Approval requiredContentWhat you’re changing🇺🇸EN🇺🇦UAPreviewTitle (EN)Short answer (EN)**An Ethernet frame** consists of a set of strictly defined fields: the destination MAC address, the source MAC address, the EtherType field, the payload, and the FCS checksum. **Key point:** when VLAN is used, a 4-byte VLAN tag (802.1Q) is added between the Source MAC and EtherType.Shown above the full answer for quick recall.Answer (EN)Image**An Ethernet frame consists of a set of strictly defined fields**, each of which performs its own task at the data link layer. --- ## Fields of an Ethernet frame ### 1. **Destination MAC address** - **6 bytes** - the MAC address of the device **the frame is intended for** - can be: - unicast - multicast - broadcast (`FF:FF:FF:FF:FF:FF`) --- ### 2. **Source MAC address** - **6 bytes** - the MAC address of the device **that sent the frame** --- ### 3. **Protocol type (EtherType)** - **2 bytes** - indicates **which protocol is inside the frame** Common values: - `0x0800`: IPv4 - `0x0806`: ARP - `0x86DD`: IPv6 --- ### 4. **Payload / Data** - **from 46 to 1500 bytes** - contains higher-layer data (usually an IP packet) If there is less than 46 bytes of data: - **padding** is added --- ### 5. **Checksum (FCS, Frame Check Sequence)** - **4 bytes** - used to **detect errors** - calculated by the sender and checked by the receiver If the FCS does not match: - the frame **is discarded** --- ## Size of an Ethernet frame Without VLAN: - **minimum**: 64 bytes - **maximum**: 1518 bytes With a VLAN tag (802.1Q): - up to **1522 bytes** --- ## VLAN tag (if used) If the network has VLANs, this is added between the Source MAC and EtherType: - **802.1Q VLAN tag**: 4 bytes - VLAN ID - priority - service information --- ## Quick summary (easy to remember) | Field | Size | |---|---| | Destination MAC | 6 bytes | | Source MAC | 6 bytes | | EtherType | 2 bytes | | Payload | 46-1500 bytes | | FCS | 4 bytes | --- ## Short version for an interview > **An Ethernet frame consists of the destination MAC address, the source MAC address, the EtherType field, the payload, and the FCS checksum; when VLAN is used, a VLAN tag is added.**For the reviewerNote to the moderator (optional)Visible only to the moderator. Helps review go faster.