BROCADE IP PRIMER

Virtual Local Area Network(VLAN)8No discussion of Layer 2 switching would be complete without mentioningVLANs. VLANs have become the foundational blocks of network infrastructuresall over the world.What is a VLAN?The acronym LAN stands for Local Area Network. This is the kind of networkmost people are familiar with. If you're using Ethernet, you are most likelydoing so within a LAN. The key word here is local. This would be your networkat home, the network that you plug your workstation into at the office, or it caneven be the network between a group of buildings geographically close to eachother. The main principle of a LAN is high-speed bandwidth and short physicaldistances. In contrast, a WAN (Wide Area Network) is geographically distant(networks between cities, countries, and even continents), and involves, typically,slower bandwidth (often involving leased long-distance circuits fromtelecommunications companies). The Internet is the largest and most wellknownWAN.Okay, so what is a VLAN? The V stands for Virtual. This is a Virtual Local AreaNetwork. “Great,” I hear you cry, “so what does that mean?!” Think of a VLANas the ability to subdivide a LAN. It can break up a LAN into, essentially,smaller LANs. These “smaller LANs” are virtual or logical LANs within a larger,physical LAN.Let's take a look at an example. Say, you have a LAN for the fictional companyH. Pete & Associates, Inc. On the fourth floor of their building, we have the Marketingdepartment and the Accounting department. All of the workstations andservers in these two departments connect to the same switch on the fourthfloor.Brocade IP Primer 169