VLAN is an acronym for Virtual Local Area Network. Several VLANs can co-exist on a single physical switch, which are configured via software (Linux commands and configuration files) and not through hardware interface (you still need to configure switch).
Virtual Local Area Networks generally referred to as VLANS are basically configured to separate the broadcast domain in a switch. Now suppose there is a switch which has 100 ports out of which 40 belong to the marketing department of a company and rest 60 belong to sales. Now if marketing department never use data broadcasted by the sales department, then there is no use sending this data to them whenever a computer in the sales department broadcast a piece of information and actually there is a disadvantage in doing so, it just encourages congestion in the network. So to solve this problem, the concept of VLANs was introduced. What VLAN will do is, it will divide a switch into two different broadcast domains, so even if somebody in sales does a broadcast, the particular data won’t go to people in marketing, which is quite advantageous.
But it’s important to remember that by default all the ports in a new switch belong to VLAN 1, and this Vlan 1 can never be deleted or edited, but we can make more VLAN and assign each port to a particular VLAN. This way the broadcast domain can be changed.
In VLAN environment if frame is going from one switch to another switch, then we need a method by which sending switch can instruct about frame’s VLAN membership to receiving switch so receiving switch must forward it through only those port which are member of same VLAN. For this we need any tagging protocol.
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