Comprehensive and Detailed in Depth Explanation:

Network segmentation, as described in NIST SP 800-171 (SC-3.13.6) and CMMC Level 2, isolates resources logically using configurations like subnets (e.g., 192.168.50.0/24), firewalls, or ACLs, not physical means. This protects engineering resources containing CUI by restricting access, despite their physical location in a shared data center. Option B (physical barriers) applies to facility security, not network isolation. Option C (encryption at rest) protects data, not network access. Option D (security badges) is irrelevant to network segmentation. Option A is the correct answer per CMMC guidelines.

Reference Extract:

NIST SP 800-171, 3.13.6:“Deny traffic by default and allow by exception through logical segmentation.”

CMMC AG Level 2, SC.L2-3.13.6:“Logical separation via network configuration isolates sensitive resources.”Resources:https://csrc.nist.gov/pubs/sp/800/171/a/final ;https://dodcio.defense.gov/Portals/0/Documents/CMMC/AG_Level2_MasterV2.0_FINAL_202112016_508.pdf