Suggest an editImprove this articleRefine the answer for “What is a VLAN?”. Your changes go to moderation before they’re published.Approval requiredContentWhat you’re changing🇺🇸EN🇺🇦UAPreviewTitle (EN)Short answer (EN)**VLAN (Virtual Local Area Network)** is a virtual local area network that lets you logically split one physical network into several isolated networks at the data link layer (L2). **Key point:** each VLAN is a separate broadcast domain, and exchanging data between VLANs requires a router or an L3 switch.Shown above the full answer for quick recall.Answer (EN)Image**VLAN (Virtual Local Area Network)** is a **virtual local area network** that lets you **logically split one physical network into several isolated networks** at the data link layer (L2). Briefly and to the point: **a VLAN is a way to split devices on one network so that they behave as if connected to different switches**, even if physically they are connected to the same one. --- ## Why VLAN is needed VLAN is used to solve several key tasks: ### 1. **Traffic isolation** Devices in different VLANs: - **do not see each other** - do not receive each other's broadcast frames - are treated as different logical networks This improves: - security - network manageability --- ### 2. **Limiting the broadcast domain** Each VLAN is: - **a separate broadcast domain** Broadcast traffic: - does not leave its own VLAN - does not load the whole network --- ### 3. **Flexibility in building a network** With VLAN: - network logic **does not depend on the physical connection** - devices can be grouped: - by department - by role - by access level Without re-cabling anything. --- ## How VLAN works technically ### VLAN ID - every VLAN is assigned a **number (VLAN ID)** - range: **1-4094** --- ### VLAN and the Ethernet frame VLAN transmission uses the **IEEE 802.1Q** standard: - a **VLAN tag (4 bytes)** is added to the Ethernet frame - the tag contains: - the VLAN ID - priority - service bits --- ## Types of switch ports ### 1. **Access port** - belongs to **one VLAN** - traffic goes **without a VLAN tag** - used to connect end devices --- ### 2. **Trunk port** - carries **traffic for several VLANs** - frames go **with VLAN tags** - used between: - switches - a switch and a router --- ## What's important to remember for an interview - VLAN works at the **data link layer (L2)** - different VLANs = different broadcast domains - to exchange data between VLANs: - a **router** or an **L3 switch** is needed - a VLAN is a **logical**, not a physical, divisionFor the reviewerNote to the moderator (optional)Visible only to the moderator. Helps review go faster.