Technology that reduces broadcast domain size In a switched network, which technology is specifically used to reduce the size of broadcast domains by logically segmenting Layer 2 networks into separate groups?

Introduction / Context:
Broadcast traffic (for example ARP) is confined to broadcast domains. In large Layer 2 networks, excessive broadcasts can degrade performance and pose security risks. VLANs allow administrators to segment a physical switch into multiple logical networks, each with its own broadcast domain, improving performance and security posture.

Given Data / Assumptions:

• The environment uses Ethernet switching.
• Goal: Reduce the scope of broadcasts.
• We are looking for the overarching technology, not just the tagging standard or loop prevention.

Concept / Approach:

VLANs (Virtual LANs) define logical Layer 2 segments. Each VLAN forms its own broadcast domain; broadcasts are not flooded across VLAN boundaries. Inter-VLAN communication requires Layer 3 routing, which provides control and filtering between segments. Standards like 802.1Q define how VLAN tags are carried over trunks, but the reduction in broadcast domain size is achieved by the VLAN segmentation itself.

Step-by-Step Solution:

Verification / Alternative check:

Monitor broadcast counters per VLAN with switch commands; you will see broadcasts are contained within each VLAN, not across the entire campus switch fabric.

Why Other Options Are Wrong:

• ISL and 802.1Q: Encapsulation/standard for tagging; they enable trunks but do not themselves define the segmentation concept.
• STP: Prevents loops; it does not reduce broadcast domain size.
• Port mirroring: Diagnostic feature; unrelated to broadcast domains.

Common Pitfalls:

• Confusing the tagging method (802.1Q) with the segmentation concept (VLANs).
• Assuming STP limits broadcast domains; it only influences topology and forwarding states.

Final Answer:

VLANs