VLAN (Virtual Local Area Network)

3 min readJun 11, 2021

What is VLAN?

A Virtual Local Area Network is created by separating a large broadcast domain into multiple smaller broadcast domains. Thus, each VLAN creates its broadcast domain.

For example:

We have a thousand PCs in a network. Now, one PC is sending an ARP packet and that ARP packet will be received by 999 PCs. What will happen? if a thousand PCs send ARP packets, it will affect the network performance. To prevent this, we can physically divide the network into two broadcast networks but we need to buy additional devices. But using VLAN we logically separate the network so it is cost-effective.

Benefits:

Reduces broadcast traffic
Improves security
Cost-effective

Range:

Registered — VLAN 0 and VLAN 4095
Default VLAN — VLAN 1
Normal — VLAN 2 to VLAN 1001
Cisco default — VLAN 1002 to VLAN 1005
Extended VLAN — VLAN 1006 to VLAN 4094

Default VLAN:

By default, all the interfaces on a switch belong to VLAN 1.

Native VLAN:

Native VLAN traffics traverse the trunk port without VLAN tags. By default, VLAN 1 is configured as Native VLAN but we can change the native VLAN configuration.

The basic purpose of native VLAN is to serve as a common identifier on opposing ends of a trunk link.

Access Port:

Access Port carries traffic for a particular VLAN. The Access port connects the PC to the switch.

Trunk Port: (802.1Q)

A trunk port carries traffic for all VLAN. The trunk port allows tagged traffic only. The port that connects switches and the uplink is configured as trunk ports.

802.1Q:

When a frame reaches the switch it is added an 802.1Q tag based on the incoming port unless it is a native VLAN.