PCSE Configuring network security Practice Question
This PCSE practice question tests your understanding of configuring network security. 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.
Your organization has a hybrid network with an on-premises data center connected to Google Cloud via a Dedicated Interconnect. The on-premises network uses RFC 1918 addresses (10.0.0.0/8) and Google Cloud VPC has a subnet in 10.1.0.0/16. You've configured a Cloud Router with BGP to exchange routes. Recently, you set up a new VPC with a subnet in 10.2.0.0/16 and peered it with the first VPC using VPC Network Peering. You notice that on-premises traffic destined to 10.2.0.0/16 is being dropped. You verify that the firewall rules allow the traffic and that BGP routes for 10.2.0.0/16 are not advertised on-premises. What should you do to enable connectivity from on-premises to the new VPC?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue: "first"
Why it matters: Order matters here. You are being tested on which action comes before the others — not which action is generally useful.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Configure the Cloud Router to advertise the 10.2.0.0/16 range via custom route advertisement.
Option B is correct because the Cloud Router uses BGP to advertise routes to the on-premises network via the Dedicated Interconnect. By default, only VPC subnet routes are advertised; custom route advertisements must be explicitly configured to propagate the peered VPC's subnet (10.2.0.0/16) to on-premises. This ensures the on-premises routers learn the route and can forward traffic to the new VPC.
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.
✗
Set up a Cloud VPN tunnel between the new VPC and on-premises.
Why it's wrong here
A VPN is not needed; the issue is route advertisement, not connectivity method.
✓
Configure the Cloud Router to advertise the 10.2.0.0/16 range via custom route advertisement.
Why this is correct
Custom route advertisements on Cloud Router propagate the peering range to on-premises.
Clue confirmation
The clue word "first" in the question point toward this answer.
Related concept
Read the scenario before looking for a memorised answer.
✗
Add a firewall rule in the new VPC allowing all traffic from 10.0.0.0/8.
Why it's wrong here
Firewall rules are not the issue; the problem is routing.
✗
Create a Shared VPC and attach the new VPC as a service project.
Why it's wrong here
Shared VPC doesn't automatically advertise routes to on-premises via Interconnect.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates assume VPC Network Peering automatically shares routes with on-premises networks via Interconnect, but in reality, peered VPC routes are not propagated to on-premises unless explicitly advertised through Cloud Router custom route advertisements.
Detailed technical explanation
How to think about this question
VPC Network Peering does not automatically propagate routes to on-premises networks connected via Dedicated Interconnect; the Cloud Router must be configured with custom route advertisements to include the peered VPC's CIDR. Under the hood, BGP updates are sent only for routes explicitly configured in the Cloud Router's advertised route list, and without this, the on-premises router's routing table lacks the 10.2.0.0/16 entry. In real-world scenarios, this often catches architects who assume peering automatically extends to all connected networks, leading to dropped traffic despite correct firewall rules.
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 healthcare organisation deploys an application with a public-facing web tier and a private database tier. The database subnet has no public IP and only accepts connections from the web tier's security group. Questions like this test whether you can design cloud network isolation using VNets/VPCs, subnets, and security group rules.
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.
Configuring network security — This question tests Configuring network security — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Configure the Cloud Router to advertise the 10.2.0.0/16 range via custom route advertisement. — Option B is correct because the Cloud Router uses BGP to advertise routes to the on-premises network via the Dedicated Interconnect. By default, only VPC subnet routes are advertised; custom route advertisements must be explicitly configured to propagate the peered VPC's subnet (10.2.0.0/16) to on-premises. This ensures the on-premises routers learn the route and can forward traffic to the new VPC.
What should I do if I get this PCSE 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: "first". Order matters here. You are being tested on which action comes before the others — not which action is generally useful.
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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