Virtual LANs
I know I keep telling you this, but I’ve got to be sure you never forget it, so here I go one last time: By default, switches break up collision domains and routers break up broadcast domains. Okay, I feel better! Now we can move on.
In contrast to the networks of yesterday, which were based on collapsed backbones, today’s network design is characterized by a flatter architecture—thanks to switches. So now what? How do we break up broadcast domains in a pure switched internetwork? By creating a virtual local area network (VLAN), that’s how!
A VLAN is a logical grouping of network users and resources connected to administratively defined ports on a switch. When you create VLANs, you gain the ability to create smaller broadcast domains within a Layer 2 switched internetwork by assigning the various ports on the switch to different subnetworks. A VLAN is treated like its own subnet or broadcast domain, meaning that frames broadcasted onto the network...
