What is VLAN

“A virtual LAN (VLAN) is a group of networking devices in the same broadcast domain, logically”

The purpose of VLANs

The basic reason for splitting a network into VLANs is to reduce congestion on a large LAN.To understand this problem, we need to look briefly at how LANs have developed over the years.Initially LANs were very flat—all the workstations were connected to a single piece of coaxial cable, or to sets of chained hubs. In a flat LAN, every packet that any device puts onto the wire gets sent to every other device on the LAN.As the number of workstations on the typical LAN grew, they started to become hopelesslycongested; there were just too many collisions, because most of the time when a workstation tried to send a packet, it would find that the wire was already occupied by a packet sent by some other device.

 VLANs address issues such as scalability, security, and network management.

Without a Router or L3 Switch, the computers within each VLAN can communicate with each other but not with any other computers in another VLAN. For example, we need a Router or L3 Switch to transfer file between VLANs. This is called “interVLAN routing”.

To allow interVLAN routing you need to configure trunking ports on the link between L3 Switch and all L2 switch.(all vlan are tagged)

Systems and others networking devices will be connected to access ports of the switch.(respective vlan are untagged)

Reference diagram as below: