This article contains a brief description of the VLAN frame tagging, how it works, etc. In the below sections all these topics are described in detail.

Frame tagging is the method used to find the VLAN (Virtual Local Area Network, which means to find whether the VLAN (Virtual Local Area Network) connected to multiple VLAN (Virtual Local Area Network) in the network, to identify it tagging is used.

The VLAN in the network which is connected may have multiple VLAN. To identify it the frame tagging is used in VLAN (Virtual Local Area Network). The VLAN (Virtual Local Area Network) contains an id named VLAN (Virtual Local Area Network) id, which is located in the frame.

When the id from the access port reaches the switch this frame is moved to the trunk link port. Each switch in the port can see the VLAN (Virtual Local Area Network) so they can identify the tag of the VLAN (Virtual Local Area Network) and moved to the corresponding VLAN (Virtual Local Area Network) access port or the trunk port of VLAN (Virtual Local Area Network). Due to this process, the end devices cannot understand the tagging.

The protocols that are used in this VLAN (Virtual Local Area Network) are discussed and provide a brief definition of it, they are :

  •       Inter-Switch Link (ISL)
  •       IEEE 802.1q


The fast ethernet and gigabit Ethernet links use a propriety protocol for their working, so for that, the protocol used is named as an inter-switch link (ISL).

Different kinds of items for a particular purpose are built using this protocol such as router interfaces, switch ports, server interface cards, etc. The inter-switch link (ISL) is propriety they can be used naturally.

This protocol will not change the Ethernet frames. 1000 VLANs can be supported by the inter-switch link (ISL) and among the transaction period, no delay occurs in the process. Per VLAN spanning tree (PVST) is the method used by the ISL (Inter-Switch Link) which is processed by SPT (Spanning Tree Protocol) and the VLAN (Virtual Local Area Network). This method allows supporting the route while they are supporting new features also.

IEEE 802.1Q

IEEE establishes the 802.1q standards, Which is used to divide the large network into small segments and then to a manageable format with the use of VLAN (Virtual Local Area Network). The methods followed to use this protocol as the easiest one are:

  • 4096 VLAN (Virtual Local Area Network) are supported
  • Without encapsulation 4 byte VLAN (Virtual Local Area Network) can be inserted
  • Compared to ISL this method has smaller frames

Because of the expanded 4 byte tag, the size is expanded from 64 bytes to 68 bytes.

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To solve the creation of VLAN (Virtual Local Area Network) over the WAN links the LAN emulation was established. This method will help the network managers to basically and logically define the workgroups other than the physical one. LANE (LAN emulation) is not much popular like ISL or IEE 802.iQ.