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Networking Fundamentals · Foundational

Broadcast Domain

The set of devices that receive each other's Layer 2 broadcasts; bounded by routers or by VLANs.

Definition

All ports in the same VLAN on interconnected switches form one broadcast domain. Each router interface or Layer 3 boundary creates a separate broadcast domain. Large broadcast domains suffer from excess broadcast traffic and wider failure impact, so networks are segmented with subnets and VLANs.

Example

A router with three LAN interfaces separates three broadcast domains.

Exam tip

Count broadcast domains by counting router interfaces (or VLANs) in the diagram.

Don't confuse it with

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