A broadcast domain is where broadcast frames travel. Switches forward broadcasts to all ports. So all devices on a switch share one broadcast domain. Routers stop broadcasts. They don't forward them between interfaces. VLANs also create separate broadcast domains within a switch. Too many devices in one broadcast domain creates noise. Your devices waste CPU processing irrelevant broadcasts.
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$ curl repovive.com/roadmaps/network-design/physical-and-data-link-fundamentals/broadcast-domains
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