11.4. Virtual LANs (VLANs)

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 ...

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