Vlan Tagging is used when a link needs to carry traffic for more than one VLAN. VLAN ( virtual local area network) is logically or simply a group of network devices.

When we create a VLAN tagging on a switch, then we actually break a broadcast domain or we can say a VLAN break broadcast domain at layer2 we use VLAN and one VLAN defines one broadcast domain.

That is the simple description about VLAN but this is not a simple in a real scenario network.

It very uses full in the big network as well as small network.

Without VLAN technology a big network can’t be handled. Now I telling about the feature, advantage and used of Vlan.

The advantage of VLAN Tagging:

  • VLAN solve the Broadcast Problem.
  • Reduce the size of the broadcast domain.
  • VLAN Allows us to add an additional layer of security.
  • By the VLAN easy to manage device management.
  • Vlan allows us to implement the logical grouping of the device by function instead of location.

The feature of VLAN Tagging:

  • To break broadcast domain at layer2 we use VLAN and one VLAN defines one broadcast domain
  • VLAN identify by a number and it is in 12bits
  • range of VLAN from 0 to 4095 (normal= 1 to 1005, extended=1006 to 4094)
  • default VLAN is vlan1 ( also called Native VLAN)
  • VLAN database save in vlan.dat file in flash to create

How to create VLAN on Switch: commands

  • switch(config)#vlan 10
  • switch(config-VLAN)#name sales
  • switch#show VLAN brief

How to assign port to any VLAN: commands

  • static VLAN assign:
  • switch(config-if)# switch port access VLAN 10
  • switch#show VLAN brief
  • switch#show VLAN id 10

By this can understand normally behave of VLAN how its configure and work. You are the networking guys or technically guys so, you know that on switch neighbour a device always there like PC, Router, Switch & WiFi etc. In between there a link, here that links also a big role. A link is two type Access link or Trunk link. What is VLAN Trunking Protocol: Read Now

A switch has compatibility to do layer2 address switching.

Access port– carries single VLAN data
Trunk port – carry multiple VLAN data

The trunk link uses the trunk encapsulation protocol, these protocol two types.

  • ISL
  • Dot.1q


  • Cisco proprietary protocol
  • It adds extra 30-byte info in existing Ethernet header. 26 byte ISL header & 4 byte ISL trailer.
  • Does not support untagged traffic
  • Does not support Native VLAN
  • MTU- 1530 byte


  • Open Standard
  • It adds 4-byte info in existing Ethernet header
  • It supports untagged traffic.
  • supports Native Vlan.
  • MTU- 1504 byte

vlan tagging

Vlan Tagging:

You can see in below picture, there is 3 VLAN available VLAN10, VLAN20 and VLAN30. Between two switches a TRUNK link used, we know that a trunk link can pass different VLAN with dot.1q encapsulation.

vlan tagging

Here we show you VLAN1o with Red Colour, VLAN20 with Green Colour & VLAN30 with Blue Colour. According to above picture, you can easily understand about VLAN tagging. When VLAN send a message then Trunk link tagged with VLAN10 (red colour only for understanding) other side trunk link remove Tagged and switch message to VLAN10 ports. Same like other VLAN data proceed with tagging and remove tagging. VLAN Tagging is used when a single link needs to carry traffic for more than one VLAN