The answer is one Cloud Router interface. This is correct because a single VLAN attachment for Dedicated Interconnect is represented by one Cloud Router interface, which serves as the logical connection point for all BGP sessions. In an active/active BGP configuration, you run two BGP sessions—one to each of the two Google Cloud routers in the pair—but both sessions are configured as sub-interfaces under that same single Cloud Router interface, not on separate interfaces. On the Google Professional Cloud Network Engineer exam, this concept tests your understanding that Cloud Router interfaces map to VLAN attachments, not to individual BGP sessions. A common trap is assuming active/active requires two interfaces because there are two routers; remember, the interface count equals the number of VLAN attachments, not the number of BGP sessions. Memory tip: “One VLAN, one interface, two sessions.”
PCNE Implementing hybrid interconnectivity Practice Question
This PCNE practice question tests your understanding of implementing hybrid interconnectivity. This is a configuration task: choose the command set that satisfies every stated requirement. Small differences — like 'secret' vs 'password' or 'transport input ssh' vs 'all' — change whether the answer is correct. 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 wants to connect their on-premises data center to Google Cloud using Dedicated Interconnect. They have ordered a 10 Gbps connection and plan to use a single VLAN attachment. How many Cloud Router interfaces are required for a single VLAN attachment with active/active BGP?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
1 interface
For a single VLAN attachment using Dedicated Interconnect with active/active BGP, only one Cloud Router interface is required. The Cloud Router interface represents the VLAN attachment itself, and BGP sessions are configured as sub-interfaces under that single interface. Active/active BGP does not require multiple interfaces; it uses two BGP sessions (one for each router in the pair) but both sessions share the same VLAN attachment and Cloud Router interface.
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.
A single VLAN attachment corresponds to one Cloud Router interface; you configure two BGP sessions on that same interface.
Related concept
Read the scenario before looking for a memorised answer.
✗
2 interfaces (one for each BGP session)
Why it's wrong here
You can have two BGP sessions on the same interface using different IP addresses.
Common exam traps
Common exam trap: answer the scenario, not the keyword
Google Cloud often tests the misconception that each BGP session requires its own interface, leading candidates to choose option D, but the correct behavior is that both sessions share the same single Cloud Router interface for a given VLAN attachment.
Detailed technical explanation
How to think about this question
Under the hood, a Cloud Router interface is a logical entity tied to a VLAN attachment, and BGP sessions are configured as sub-interfaces (e.g., interface 0 with BGP peers 169.254.0.1/29 and 169.254.0.2/29). In active/active BGP, both sessions are established over the same VLAN attachment, and the Cloud Router interface handles both sessions. A real-world scenario where this matters is when using multiple VLAN attachments for redundancy; each VLAN attachment gets its own Cloud Router interface, but within a single attachment, only one interface is needed regardless of the number of BGP sessions.
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: 1 interface — For a single VLAN attachment using Dedicated Interconnect with active/active BGP, only one Cloud Router interface is required. The Cloud Router interface represents the VLAN attachment itself, and BGP sessions are configured as sub-interfaces under that single interface. Active/active BGP does not require multiple interfaces; it uses two BGP sessions (one for each router in the pair) but both sessions share the same VLAN attachment and Cloud Router interface.
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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