The answer is to upgrade the edge routers to models that support hardware-accelerated IPsec encryption. This is correct because high CPU usage on edge routers is a classic symptom of software-based IPsec encryption overwhelming the processor, which directly causes the reported latency and packet loss. Hardware offload shifts the cryptographic operations to dedicated ASICs or crypto engines, eliminating the processing bottleneck and reducing IPsec high CPU latency without altering the security policy or requiring major operational changes. On the CISSP exam, this scenario tests your understanding of network security architecture and the trade-offs between performance and encryption—a common trap is choosing to reduce encryption strength or switch to a less secure protocol, which violates the mandated security policy. Remember the mnemonic “CPU Crunch? Offload the Punch” to recall that hardware offload solves performance issues without compromising security.
CISSP Communication and Network Security Practice Question
This CISSP practice question tests your understanding of communication and network security. The scenario asks you to isolate a root cause — eliminate options that address a different problem before choosing. After answering, compare your reasoning against the explanation and wrong-answer breakdown below. Once you have made your selection, read the full explanation to reinforce the concept and understand why each distractor is designed to mislead on exam day.
You are the security architect for a global financial firm. The organization has recently deployed a new cloud-based application that requires low-latency connections between data centers in New York, London, and Tokyo. The existing WAN uses MPLS L3 VPNs with IPsec encryption. However, the application team reports excessive latency and packet loss during peak hours. The network team confirms that the MPLS links are underutilized, but the IPsec tunnels show high CPU usage on the edge routers. Additionally, the security policy mandates that all inter-data center traffic must be encrypted and authenticated. The firm has a budget for hardware upgrades but wants to minimize operational changes. Which of the following is the BEST course of action?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue: "best"
Why it matters: Signals that multiple options may be partially correct. Choose the option that most directly solves the exact problem described, not the one that sounds most complete.
Clue: "minimum / minimize"
Why it matters: Asks for the least resource use — fewest addresses, smallest subnet, lowest overhead. Eliminate over-provisioned options even if they would technically work.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Upgrade the edge routers to models that support hardware-accelerated IPsec encryption.
Option D is correct because the high CPU usage on edge routers is a classic symptom of software-based IPsec encryption overwhelming the router's CPU. Hardware-accelerated IPsec offloads the cryptographic operations to dedicated ASICs or crypto engines, reducing CPU load and eliminating the latency and packet loss caused by processing bottlenecks. This directly addresses the root cause without changing the security policy or requiring major operational changes.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
✗
Reduce the IPsec encryption algorithm to AES-128 and the hash to SHA-1 to lower CPU usage.
Why it's wrong here
Weakens security and may not be compliant with policy.
✗
Replace MPLS with dedicated point-to-point circuits and remove IPsec encryption.
Why it's wrong here
Removing encryption violates security policy and increases cost.
✗
Increase the MTU on the WAN interfaces to reduce packet fragmentation.
Why it's wrong here
MTU adjustment may help fragmentation but does not address CPU overload.
✓
Upgrade the edge routers to models that support hardware-accelerated IPsec encryption.
Why this is correct
Hardware offloading reduces CPU load and improves performance.
Clue confirmation
The clue words "best", "minimum / minimize" in the question point toward this answer.
Related concept
Read the scenario before looking for a memorised answer.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates mistakenly think reducing encryption strength (Option A) will solve CPU issues, but the CISSP exam tests that hardware offload is the proper solution when CPU is the bottleneck, not the algorithm choice.
Detailed technical explanation
How to think about this question
Hardware-accelerated IPsec uses dedicated cryptographic processors (e.g., Cisco's Crypto Engine or QAT on Intel chips) to handle AES, SHA, and DH operations, achieving line-rate encryption without taxing the main CPU. In contrast, software-based IPsec on routers like Cisco ISR 4000 series can cause CPU spikes above 90% under load, leading to queuing delays and drops. Real-world deployments often show latency dropping from 50ms to under 5ms after enabling hardware offload, as the router can process packets at wire speed.
KKey Concepts to Remember
Read the scenario before looking for a memorised answer.
Find the constraint that changes the correct option.
Eliminate answers that are true in general but not in this case.
TExam Day Tips
→Watch for words such as best, first, most likely and least administrative effort.
→Review why wrong options are wrong, not only why the correct option is correct.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
How this comes up in practice
A developer is choosing between AES-256 (symmetric) and RSA-2048 (asymmetric) for encrypting a large file that will be sent to a partner. Symmetric encryption is fast but requires key exchange; asymmetric is slower but solves the key distribution problem. A hybrid approach — encrypt the file with AES, encrypt the AES key with RSA — is standard. Questions like this test whether you understand when each approach applies.
Related glossary terms
Concepts from this question explained
These glossary pages explain the core terms tested in this CISSP question in full detail.
Communication and Network Security — This question tests Communication and Network Security — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Upgrade the edge routers to models that support hardware-accelerated IPsec encryption. — Option D is correct because the high CPU usage on edge routers is a classic symptom of software-based IPsec encryption overwhelming the router's CPU. Hardware-accelerated IPsec offloads the cryptographic operations to dedicated ASICs or crypto engines, reducing CPU load and eliminating the latency and packet loss caused by processing bottlenecks. This directly addresses the root cause without changing the security policy or requiring major operational changes.
What should I do if I get this CISSP question wrong?
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Are there clue words in this question I should notice?
Yes — watch for: "best", "minimum / minimize". Signals that multiple options may be partially correct. Choose the option that most directly solves the exact problem described, not the one that sounds most complete.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
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