VLAN Tag & Untag Concepts and Differences

In this session, we will learn about Tag & Untag, which is commonly used in VLANs.

 

For those who studied vlan, you must understand the next step, tag & untag, so that you won't be confused when setting up the equipment. If you don't know what VLAN is yet, go to the link below and get used to it.

 

 

1. Tag & Untag Concepts

 

 

Those who are studying network for the first time have often seen words like tag, untag, access, trunk.But it's also a confusing term that I don't understand.

 

It can be more confusing for beginners who start studying with Cisco equipment. Because Cisco uses its own Protocol unlike other vendors' equipment, so the terminology is not standard, but its own.

 

 

So, we use terms like access list, trunk, etherchannel, etc.

 

 

If I explain tag and untag easily without confusing all the difficult words ▶

 

① Untag

: Creating a path through which only one Vlan can pass (Standard Protocol)

 

② Tag

: Creating a Path for Multiple Vlans to Pass (Standard Protocol)

 

③ Access link

: Creating a path through which only one Vlan can pass = untag

(Non-standard - proprietary Cisco Protocol for use with Cisco equipment only)

 

④ Trunk link

: Making way for multiple Vlan's to pass = Tag

(Non-standard - proprietary Cisco Protocol for use with Cisco equipment only)

 

 

 

Description of the picture above

 

 

Untag Communications

 

 

①PC and PC PC communication is possible: It has created a way for only one vlan to communicate.

 

③PC and PC PC communication is possible

 

 

 

tag communication

 

: Connect one cable between two switches and set it to Tag

 

 

One cable made way for two vlan bands, 192.168.100.0 / 192.168.200.0

 

 

Tag communicates with a recognition number when communicating. Please remember that.

 

 

 

 

Configuring Exceptions

 

 

 

 

 

 In the picture above, is it possible to communicate with PC PC and PC PC?

 

Let's think it over and find the answer.

 

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The answer is no communication.Tag communicates with an identification number, explained above.

 

 

Since the PC cannot recognize the identification number of the tag, as shown in the figure above, the port 6 of the switch is connected to the PCPC, the connection port is set to Tag, so the PC cannot recognize the tag number. The port to which the PC is connected must be an untag port for communication.

 

The IPT phone recognizes the Tag. [Switch == IPT phone == PC] I've been using IPT phones a lot these days, and I see this configuration a lot.

 

 

Usually, IPT phones and PCs have different IP Address bands. The IPT phone recognizes the Tag. The tag is not recognized by the PC or general equipment.

 

 

Tag and untag are very easy to understand, but if you try to memorize it without understanding, you may have difficulties in various configurations or designs in the actual field, so please think about it and make it your own.

 

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