Chapter 2. VLANs

VLAN Overview

A physical network segment is a group of devices that shares the same physical wire. They can communicate directly with each other. A virtual LAN (VLAN) is a logical network segment. It is a way to group devices so that they can communicate at Layer 2 even though they might be physically separate. Switch ports assigned to the same VLAN create a virtual LAN, sharing a broadcast (and multicast) domain regardless of their physical locations in the switched network. A switch can have multiple VLANs, in which case frames are only forwarded to other ports within the same VLAN. For traffic to move between VLANs requires a Layer 3 process, and thus either a router or a multilayer switch. VLAN membership can be assigned ...

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