Network Engineering Basics: In-Depth VLAN and Trunk Theory | CCNA EXAM GUIDE

Original author：B.S Academy

Original source：https://www.youtube.com/embed/NnEmF0MkNos

visit: https://emcglobal.in For full tech courses and more networking resources, Here is a concise breakdown of VLANs, Trunks, ranges, and port modes. 1. Functioning: VLANs & Trunks VLAN (Virtual LAN): Logically divides a single physical switch into multiple independent broadcast domains. Devices in the same VLAN can communicate directly, while devices in different VLANs need a router or Layer 3 switch to communicate. This improves security and reduces unnecessary broadcast traffic. Trunk Link: A point-to-point link between two network devices (usually switch-to-switch or switch-to-router) that carries traffic for multiple VLANs over a single physical cable. It uses IEEE 802.1Q to insert a 4-byte tag into the Ethernet frame, identifying which VLAN the packet belongs to. 2. VLAN Ranges (1–4094) 0 & 4095: Reserved (cannot be used). 1: Default VLAN and default Native VLAN. 2 – 1001: Normal Range (used for everyday configurations). 1002 – 1005: Reserved for legacy protocols (FDDI and Token Ring). 1006 – 4094: Extended Range (requires VTP Transparent mode in Cisco environments; commonly used in service provider or large enterprise networks). 3. Port Modes Access Mode (switchport mode access): The port belongs to a single, specific VLAN. Untagged traffic enters and leaves this port. It connects to end devices like PCs, servers, or printers. Trunk Mode (switchport mode trunk): The port is forced to carry multiple VLANs and expects 802.1Q tagged frames.