Switching and Broadcast Domains — 12-Port Unmanaged Switch In computer networking fundamentals, if you segment a small local area network (LAN) using a single unmanaged Layer 2 Ethernet switch that has 12 physical ports and you do not configure any Virtual LANs (VLANs), how many broadcast domains are created by this switch?

Introduction / Context:
Understanding broadcast domains is essential for designing scalable and efficient networks. A broadcast domain is the set of devices that receive a Layer 2 broadcast frame (destination MAC FF:FF:FF:FF:FF:FF). This question checks whether you can differentiate the behavior of hubs, switches, routers, and VLANs with respect to broadcast containment.

Given Data / Assumptions:

• A single Layer 2 Ethernet switch with 12 ports is used.
• No VLANs are configured; the switch is operating in a default, single-VLAN state.
• No routers or Layer 3 interfaces are present to segment broadcasts.

Concept / Approach:
Switches break up collision domains per port (full-duplex eliminates collisions), but they do not break up broadcast domains by default. Only routers (or Layer 3 switches performing inter-VLAN routing) and VLAN boundaries segment broadcast domains. Therefore, an unmanaged or default-configured Layer 2 switch, regardless of port count, creates one broadcast domain. The number of ports affects collision domains, not broadcast domains, unless VLANs are configured.

Step-by-Step Solution:
Identify device type: Layer 2 switch, default configuration.Recall rule: Switch = many collision domains (per port) but a single broadcast domain unless VLANs are used.Note that routers or Layer 3 interfaces are required to segment broadcasts.Conclude that the entire switch is one broadcast domain in the default state.

Verification / Alternative check:
Create two VLANs (for example, VLAN 10 and VLAN 20) and assign ports to them; you will now have two broadcast domains. With no VLANs, only one exists across all 12 ports.

Why Other Options Are Wrong:

• 2, 5, 12: These imply VLAN or Layer 3 segmentation, which is not present.
• 0: Impossible; any Layer 2 segment forms at least one broadcast domain.

Common Pitfalls:
Confusing collision domains (per switch port) with broadcast domains (per VLAN or Layer 3 boundary). Also assuming the number of ports equals the number of broadcast domains, which is incorrect without VLANs.

Final Answer:
1