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CAS-004 Practice Question: Designing a new data center with high…

A company is designing a new data center with high availability requirements. The network team proposes using virtualized network functions (VNFs) on commodity hardware to reduce costs. Which security consideration is MOST important when implementing this design?

⚠ Common exam trap

Candidates often confuse operational requirements (redundancy, QoS, encryption) with security controls, overlooking that isolation is the foundational security measure in a shared virtualized environment.

Answer choices

Why each option matters

Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.

Correct answer & explanation

Isolate VNFs to prevent lateral movement if one VNF is compromised

Isolating VNFs is the most important security consideration because VNFs share the same hypervisor and commodity hardware, so a compromise in one VNF could allow an attacker to move laterally to other VNFs or the underlying host. Without proper isolation (e.g., using VLANs, VXLANs, or micro-segmentation), the entire multi-tenant environment is at risk, undermining the high-availability design.

Answer analysis

Option-by-option breakdown

For each option: why learners choose it and why it is or isn't the right answer here.

  • Isolate VNFs to prevent lateral movement if one VNF is compromised

    Why this is correct

    Isolation is critical because VNFs share hypervisor; a compromise could spread.

  • Ensure VNFs are deployed across multiple physical hosts for redundancy

    Why it's wrong here

    Redundancy is a design goal but not the most important security consideration.

  • Encrypt all traffic between VNFs to prevent eavesdropping

    Why it's wrong here

    Encryption is important but not the most critical security consideration for VNF sharing.

  • Implement quality of service (QoS) to guarantee bandwidth for critical VNFs

    Why it's wrong here

    QoS addresses performance, not security.

Visual reference

Switch VLAN 10 Sales (192.168.10.0/24) PC-A PC-B VLAN 20 HR (192.168.20.0/24) PC-C PC-D Router VLANs isolate traffic — inter-VLAN routing requires a Layer 3 device

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JA

Written by Johnson Ajibi, MSc IT Security

Senior Network & Security Engineer · founder of Courseiva

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