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IEEE 802 1Q: Tagging and Trunking 101
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IEEE 802 1Q: Tagging and Trunking 101

Understanding VLAN Tagging and Trunking Basics

Introduction to VLAN Tagging

  • Sunny introduces the topic of VLAN tagging and trunking basics, referencing the Igoe A Oh 2001 Q standard.
  • The discussion begins with an explanation of how traffic is managed between switches using VLANs, emphasizing that each switch maintains its own local VLAN information.

Understanding Trunks and Ports

  • A trunk link is defined as a connection that allows multiple VLAN traffic to traverse between switches, enabling communication for devices on the same VLAN across different switches.
  • By default, a trunk can carry all VLAN traffic but can be configured to limit which specific VLANs are allowed through it.
  • The term "trunk port" (or "tag port" in Cisco terminology) refers to ports configured to add a VLAN tag to Ethernet frames, indicating their respective VLAN.

Access Ports vs. Trunk Ports

  • An access port (or untagged port) is designed for single-VLAN traffic and does not expect any tags; it only carries traffic for one specific VLAN.
  • To facilitate communication between computers on different switches within the same VLAN, trunks must be established by configuring trunk ports.

Frame Transmission Process

  • When Computer A sends a frame without any inherent VLAN information, it relies on switch configurations to identify its source and destination based on membership in a specific VLAN.
  • Switch 1 recognizes that Computer A belongs to VLAN 10 and prepares the frame for transmission over the trunk link by inserting a corresponding VLAN tag.

Tagging Process Explained

  • The tagging process involves adding four fields into the Ethernet frame: identification of the frame type, quality of service data, a reserved bit set to zero, and the actual VLAN identifier ranging from 1 to 4094.
  • Once tagged, this modified frame becomes known as an IEEE 802.1Q frame; tagging or encapsulation refers specifically to this addition of information into the original Ethernet frame.

Conclusion and Future Topics

  • The video concludes with an analogy comparing trunks to highways where each lane represents different types of traffic (VLAN), highlighting how frames are forwarded based on their tags.
Video description

IEEE 802.1Q: Tagging and trunking 101 Today my topic is IEEE 802.1q standard: tagging and trunking basics. I talk about many terminologies such as VLAN tag, tagging, encapsulation, trunk, trunking, trunk port, and an access port. I will use an example to show what they are and how they work. The IEEE 802.1q, often referred to as Dot1q, is the networking standard that supports VLANs on the Ethernet network. The standard defines a method of tagging traffic between two switches to tell which traffic belongs to which VLAN. Keep in mind, there are many implementations of IEEE 8021.q standard, but we tend to talk more about using Cisco switches. My whole playlists: https://www.youtube.com/user/sunnylearning/playlists Related Playlists Virtualization, VLAN, Trunking, VPN https://www.youtube.com/playlist?list=PLSNNzog5eydurp2zcB4xs6gdeeVW3cMOW&playnext=1&index=1&disable_polymer=true Switching and Routing https://www.youtube.com/watch?v=ck3gx9HB9-k&list=PLSNNzog5eydtmcbcbc1b8pVRkgre3vNUy Ethernet Basics https://www.youtube.com/playlist?list=PLSNNzog5eydvAxPHJiDybPomC1fFHf1KE