The answer is that BGP multipath is enabled, causing all traffic to be sent through the remaining tunnel. This is the most likely explanation because when BGP multipath is active on an HA VPN with active-active BGP sessions, the router load-balances traffic across multiple tunnels under normal conditions. When one tunnel fails, the router loses the multipath routes and shifts all traffic to the single surviving tunnel, which can quickly become congested or force traffic over a suboptimal path, directly increasing latency. On the Google Professional Cloud Network Engineer exam, this question tests your understanding of how BGP multipath interacts with HA VPN tunnel failures—a common trap is assuming the remaining tunnel handles traffic identically, when in reality the loss of load distribution creates a bottleneck. A useful memory tip: think of multipath as a highway with two lanes; when one lane closes, all cars merge into the remaining lane, causing a traffic jam and slower travel times.
PCNE Implementing hybrid interconnectivity Practice Question
This PCNE practice question tests your understanding of implementing hybrid interconnectivity. 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.
An organization uses HA VPN with dynamic routing and active-active BGP sessions. One tunnel fails, but traffic continues to flow through the other tunnel. However, they notice increased latency. What is the most likely explanation?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue: "most likely"
Why it matters: Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
BGP multipath is enabled, causing all traffic to be sent through the remaining tunnel.
When BGP multipath is enabled on an HA VPN with active-active BGP sessions, the router can load-balance traffic across multiple tunnels. If one tunnel fails, all traffic is redirected through the remaining tunnel, which can cause increased latency due to congestion or suboptimal path selection. The correct answer is A because this behavior directly explains the latency increase after a tunnel failure.
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.
✓
BGP multipath is enabled, causing all traffic to be sent through the remaining tunnel.
Why this is correct
With multipath, traffic is normally split; after failure, all traffic goes through one tunnel, potentially causing congestion.
Clue confirmation
The clue word "most likely" in the question point toward this answer.
Related concept
Read the scenario before looking for a memorised answer.
✗
The remaining tunnel is using a different encryption algorithm.
Why it's wrong here
Encryption algorithm affects security, not latency.
✗
The BGP timers are misconfigured.
Why it's wrong here
Timer misconfiguration would cause session flapping, not increased latency.
✗
The failed tunnel's routes are still in the routing table.
Why it's wrong here
Routes should be withdrawn when the tunnel fails.
Common exam traps
Common exam trap: answer the scenario, not the keyword
Google Cloud often tests the misconception that increased latency after a tunnel failure is due to routing table issues or encryption changes, when in fact it is the result of BGP multipath concentrating all traffic onto a single tunnel, causing congestion.
Detailed technical explanation
How to think about this question
In HA VPN with dynamic routing, BGP multipath (enabled via the `maximum-paths` command) allows multiple equal-cost paths to be installed in the routing table. When one tunnel fails, BGP withdraws its routes, and the remaining tunnel carries all traffic, potentially exceeding its bandwidth capacity or causing queueing delays. This is distinct from ECMP load balancing, where traffic is distributed proportionally; without multipath, only one path would be used, and failure would simply switch to the other without a latency spike unless the remaining path is inherently slower.
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 cloud solutions architect for a retail company is evaluating services for a new workload. The correct answer here reflects best practice for the specific scenario described — not a general cloud recommendation. Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option. Cloud exam questions reward reading the constraint carefully: the same technology can be right or wrong depending on the use case.
What to study next
Got this wrong? Here's your next step.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Implementing hybrid interconnectivity — This question tests Implementing hybrid interconnectivity — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: BGP multipath is enabled, causing all traffic to be sent through the remaining tunnel. — When BGP multipath is enabled on an HA VPN with active-active BGP sessions, the router can load-balance traffic across multiple tunnels. If one tunnel fails, all traffic is redirected through the remaining tunnel, which can cause increased latency due to congestion or suboptimal path selection. The correct answer is A because this behavior directly explains the latency increase after a tunnel failure.
What should I do if I get this PCNE 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: "most likely". Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
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Question Discussion
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