The answer is to provision two VLAN attachments on two separate Cloud Routers in different zones. This configuration is required because Google Cloud’s Dedicated Interconnect high availability SLA demands redundancy at both the network and compute layers; a single VLAN attachment or Cloud Router creates a single point of failure, whereas two attachments on distinct routers in different zones ensure that traffic can fail over if one zone or router goes down. On the Google Professional Cloud Network Engineer exam, this concept tests your understanding of the 99.99% availability SLA for Dedicated Interconnect, often appearing as a trap where candidates mistakenly think a single router with two attachments suffices. The key memory tip is “two zones, two routers, two attachments” — think of it as a three-legged stool where each leg must be independent to avoid collapse.
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 is deploying a Dedicated Interconnect with a 10 Gbps circuit to Google Cloud. They need to ensure high availability. Which configuration is required by Google Cloud to meet the high availability SLA?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Provision two VLAN attachments on two separate Cloud Routers in different zones
To meet the high availability SLA for Dedicated Interconnect, Google Cloud requires at least two VLAN attachments, each on a separate Cloud Router in different zones. This ensures that if one zone or Cloud Router fails, traffic can still flow through the other attachment, providing redundancy. A single VLAN attachment or a single Cloud Router does not meet the 99.99% availability SLA because it creates a single point of 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.
✗
Combine Dedicated Interconnect with a Cloud VPN tunnel for failover
Why it's wrong here
Cloud VPN is not required for Dedicated Interconnect HA; two VLAN attachments suffice.
✗
Use Partner Interconnect instead of Dedicated Interconnect
Why it's wrong here
Partner Interconnect is a different service and not required for Dedicated Interconnect HA.
✓
Provision two VLAN attachments on two separate Cloud Routers in different zones
Why this is correct
Two VLAN attachments in different zones provide redundancy and meet the HA SLA.
Related concept
Read the scenario before looking for a memorised answer.
✗
Provision a single VLAN attachment on one Cloud Router
Why it's wrong here
A single VLAN attachment does not provide redundancy.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates often think a single Cloud Router with multiple VLAN attachments is sufficient, but Google Cloud requires the Cloud Routers themselves to be in different zones to avoid a single point of failure at the zone level.
Detailed technical explanation
How to think about this question
Under the hood, each VLAN attachment corresponds to a BGP session on a Cloud Router, and Google Cloud's high availability SLA requires that these sessions be established in at least two different zones (e.g., us-central1-a and us-central1-b). This ensures that if a zone fails, the BGP session in the other zone continues to advertise routes, maintaining connectivity. In a real-world scenario, if you only have one VLAN attachment and the zone goes down, your on-premises network loses all connectivity to Google Cloud, violating the 99.99% 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: Provision two VLAN attachments on two separate Cloud Routers in different zones — To meet the high availability SLA for Dedicated Interconnect, Google Cloud requires at least two VLAN attachments, each on a separate Cloud Router in different zones. This ensures that if one zone or Cloud Router fails, traffic can still flow through the other attachment, providing redundancy. A single VLAN attachment or a single Cloud Router does not meet the 99.99% availability SLA because it creates a single point of 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.
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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