The answer is two VLAN attachments, each on a different Interconnect. This configuration is required to meet the dedicated interconnect 99.99% SLA because a single VLAN attachment on one Interconnect creates a single point of failure; Google Cloud’s SLA for Dedicated Interconnect mandates redundant physical paths to guarantee that availability level. On the Google Professional Cloud Network Engineer exam, this tests your understanding of high-availability design for hybrid connectivity, often appearing as a trap where candidates mistakenly think one VLAN attachment with multiple tunnels suffices. The key is that the SLA requires two physically separate Interconnects—ideally in different edge availability domains—so that a fiber cut or device failure on one link does not disrupt traffic. A simple memory tip is “two links, two lives”: always provision two distinct Interconnects with one VLAN attachment each to achieve the 99.99% uptime promise.
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.
A company needs to connect their on-premises data center to Google Cloud using Dedicated Interconnect. They have a service level agreement that requires 99.99% availability for the connection. What is the minimum number of VLAN attachments they must provision, and how should they be configured to meet this SLA?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
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
✓
Two VLAN attachments, each on a different Interconnect
To achieve 99.99% availability for Dedicated Interconnect, you must eliminate single points of failure. A single VLAN attachment on one Interconnect (Option A) provides no redundancy. Google Cloud requires at least two VLAN attachments, each on a different Interconnect (and ideally different edge availability domains), to meet this SLA. This ensures that if one Interconnect or VLAN attachment fails, traffic can fail over to the other, maintaining connectivity.
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.
✗
One VLAN attachment with a single Interconnect
Why it's wrong here
A single connection does not provide redundancy and cannot meet 99.99% SLA.
✓
Two VLAN attachments, each on a different Interconnect
Why this is correct
Two VLAN attachments on redundant Interconnects provide the required availability.
Clue confirmation
The clue word "minimum / minimize" in the question point toward this answer.
Related concept
Read the scenario before looking for a memorised answer.
✗
Four VLAN attachments on two Interconnects
Why it's wrong here
This exceeds the minimum requirement; two VLAN attachments (one per Interconnect) are sufficient for 99.99%.
✗
Two VLAN attachments on the same Interconnect
Why it's wrong here
Redundancy requires separate Interconnects, not just separate VLAN attachments.
Common exam traps
Common exam trap: answer the scenario, not the keyword
Google Cloud often tests the misconception that two VLAN attachments on the same Interconnect provide redundancy, but the trap here is that they share the same physical link and edge availability domain, so a single failure takes down both attachments.
Detailed technical explanation
How to think about this question
Under the hood, each Dedicated Interconnect connection terminates at a Google Cloud edge availability domain (a specific metro location with redundant power and network). For 99.99% availability, you must provision two Interconnects, each in a different edge availability domain, and attach a separate VLAN attachment to each. This design allows BGP sessions to fail over via dynamic routing (e.g., using AS-path prepending or local preference) if one link or attachment fails. In a real-world scenario, if you only use one Interconnect, a fiber cut or maintenance event could cause a complete outage, violating the SLA.
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
An e-commerce site experiences heavy traffic on Black Friday and near-zero traffic during off-peak weeks. Rather than provisioning permanent large VMs, the team uses auto-scaling groups that add capacity automatically under load and reduce it overnight. Questions like this test whether you understand elasticity, availability zones, and cloud compute scaling patterns.
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: Two VLAN attachments, each on a different Interconnect — To achieve 99.99% availability for Dedicated Interconnect, you must eliminate single points of failure. A single VLAN attachment on one Interconnect (Option A) provides no redundancy. Google Cloud requires at least two VLAN attachments, each on a different Interconnect (and ideally different edge availability domains), to meet this SLA. This ensures that if one Interconnect or VLAN attachment fails, traffic can fail over to the other, maintaining connectivity.
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: "minimum / minimize". Asks for the least resource use — fewest addresses, smallest subnet, lowest overhead. Eliminate over-provisioned options even if they would technically work.
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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