Suggest an editImprove this articleRefine the answer for “What is an Ethernet frame?”. Your changes go to moderation before they’re published.Approval requiredContentWhat you’re changing🇺🇸EN🇺🇦UAPreviewTitle (EN)Short answer (EN)**An Ethernet frame** is the unit of data transmission on Ethernet networks at the data link layer (L2), the form in which data moves between devices within a single local network. **Key point:** a frame contains the destination and source MAC addresses, a type field (EtherType), a payload, and a checksum (FCS) for detecting errors.Shown above the full answer for quick recall.Answer (EN)Image**An Ethernet frame** is the **unit of data transmission on Ethernet networks at the data link layer (L2)**. Data is transmitted **between devices within a single local network** precisely in the form of Ethernet frames. Briefly: **An Ethernet frame is the format Ethernet uses to package and transmit data**. --- ## Why an Ethernet frame is needed The physical layer transmits only bits. An Ethernet frame is needed to: - mark **the start and end of the data** - specify **the recipient's and sender's MAC address** - identify **which protocol is inside** - check **whether the data is corrupted** --- ## Structure of an Ethernet frame A classic Ethernet II frame consists of the following fields: ### 1. **Destination MAC address** - 6 bytes - indicates **who the frame is intended for** - can be unicast, multicast, or broadcast --- ### 2. **Source MAC address** - 6 bytes - the MAC address of the sending device --- ### 3. **Type (EtherType)** - 2 bytes - shows **which protocol is inside the frame** Examples: - `0x0800`: IPv4 - `0x0806`: ARP - `0x86DD`: IPv6 --- ### 4. **Payload** - from **46 to 1500 bytes** - usually contains an **IP packet** - if there is less than 46 bytes of data, padding is added --- ### 5. **Checksum (FCS)** - 4 bytes - used to **detect errors** - if the check fails, the frame is discarded --- ## Size of an Ethernet frame - **Minimum**: 64 bytes - **Maximum**: 1518 bytes (without a VLAN tag) With a VLAN tag: - up to **1522 bytes** --- ## Where an Ethernet frame is used Ethernet frames: - are used on **wired Ethernet networks** - are also used as the basis for Wi-Fi (with a format conversion) - exist **only within a single local network** When passing through a router: - the Ethernet frame **is discarded** - a **new frame** is created for the next network segment --- ## What matters for an interview - an Ethernet frame is **L2** - an **L3 packet** is contained inside the frame - switches work **specifically with Ethernet frames** - routers **do not forward frames**, they **rebuild** them --- ## Short version for an interview > **An Ethernet frame** is the data link layer's data format, used on Ethernet networks, containing MAC addresses, service fields, and a payload for transmitting data within a local network.For the reviewerNote to the moderator (optional)Visible only to the moderator. Helps review go faster.