A technology called VLAN (Virtual LAN broadcast domains logically segmented on an Ethernet switch) trunking that was once primarily the domain of network switches has now trickled down to the rest of the Data Center to address these issues. Now it is possible for these multi-homing devices to be multi-homing in function without the need for multiple physical network adapters and the additional infrastructure associated with them. VLAN trunking allows a single network adapter to behave as ?n? number of virtual network adapters, where ?n? has a theoretical upper limit of 4096 but is typically limited to 1000 VLAN network segments. In the case where a single gigabit Ethernet adapter is trunked in place of using multiple FastEthernet adapters, higher performance at a lower cost while increasing flexibility can be achieved. This really is the best of all worlds. In this article, I will give you an overview of VLAN trunking, how it works what it is used for.
VLAN is a technology by which we can administratively assign different ports of the same layer2 switch to different subnetworks. This is particularly useful when different departments of a company have offices in different floors of the same office. The different departments can be connected via a layer2 switch , which is having configuration for other subnetwork also. So practically the same switch acts as if it is more than one. Packets destined for the specific subnetwork are forwarded to those ports only. But the switch does not make any routing decisions. For interconnecting different subnetworks, routers are needed.
VLAN essentially provides segmentation between different subnetworks.