VLAN Basics

Figure 11-1 shows how layer 2 switched networks are typically designed—as flat networks. With this configuration, every broadcast packet transmitted is seen by every device on the network regardless of whether the device needs to receive that data or not.

Figure 11-1: Flat network structure

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By default, routers allow broadcasts to occur only within the originating network, while switches forward broadcasts to all segments. Oh, and by the way, the reason it’s called a flat network is because it’s one broadcast domain, not because the actual design is physically flat. In Figure 11-1 we see Host A sending out a broadcast and all ports ...

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