- A
The peering connection is in an inactive state
Why wrong: Inactive peering would break connectivity entirely, not cause asymmetry.
- B
The firewall rules in Network A are more permissive than in Network B
Why wrong: Firewall rules do not affect routing paths.
- C
There is a Cloud NAT configured in Network A but not in Network B
Why wrong: NAT is for outbound internet, not internal peering.
- D
Both VPCs have a default route (0.0.0.0/0) pointing to different next hops
Different default routes can cause traffic to exit via different gateways, breaking symmetry.
Question 439 of 1,000
PCNE Practice Question: Managing, Monitoring, and Optimising Network Operations
This PCNE practice question tests your understanding of managing, monitoring, and optimising network operations. Match the stated requirement to the specific cloud service, access model, or configuration option — many options are valid in isolation but not for this scenario. 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 has two VPC networks connected via VPC peering. They notice asymmetric routing: traffic from Network A to Network B follows one path, but return traffic from B to A takes a different path. This is causing connectivity issues for stateful firewalls. What is the likely cause?
Answer choices
Why each option matters
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Both VPCs have a default route (0.0.0.0/0) pointing to different next hops
VPC peering does not enforce symmetric routing by default. If both networks have subnet CIDRs that overlap, or if one network has a route that sends traffic to the other via a different next hop (e.g., VPN or NAT), asymmetric routing can occur. The most common cause is when both VPCs have a default route pointing to different next hops (e.g., one to the internet, one to a VPN), causing different paths.
Key principle: Count usable hosts — not total addresses — and remember that the network and broadcast addresses are not available to hosts in standard IPv4 subnets.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
The peering connection is in an inactive state
Why it's wrong here
Inactive peering would break connectivity entirely, not cause asymmetry.
- ✗
The firewall rules in Network A are more permissive than in Network B
Why it's wrong here
Firewall rules do not affect routing paths.
- ✗
There is a Cloud NAT configured in Network A but not in Network B
Why it's wrong here
NAT is for outbound internet, not internal peering.
- ✓
Both VPCs have a default route (0.0.0.0/0) pointing to different next hops
Why this is correct
Different default routes can cause traffic to exit via different gateways, breaking symmetry.
Related concept
CIDR notation defines the prefix length.
Common exam traps
Common exam trap: usable hosts are not the same as total addresses
Subnetting questions often tempt you into counting all addresses. In normal IPv4 subnets, the network and broadcast addresses are not usable host addresses.
Detailed technical explanation
How to think about this question
Subnetting questions test whether you can identify the network, broadcast address, usable range, mask and correct subnet. Slow down enough to calculate the block size correctly.
KKey Concepts to Remember
- CIDR notation defines the prefix length.
- Block size helps identify subnet boundaries.
- Network and broadcast addresses are not usable hosts in normal IPv4 subnets.
- The required host count determines the smallest suitable subnet.
TExam Day Tips
- Write the block size before choosing the subnet.
- Check whether the question asks for hosts, subnets or a specific address range.
- Do not confuse /24, /25, /26 and /27 host counts.
Key takeaway
Count usable hosts — not total addresses — and remember that the network and broadcast addresses are not available to hosts in standard IPv4 subnets.
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.
Visual reference
Quick reference
Asymmetric Encryption Algorithm Comparison
| Algorithm | Key Exchange | Signatures | Equivalent Security Key | Notes |
|---|---|---|---|---|
| RSA-3072 | Yes | Yes | 128-bit | Widely deployed; slow for bulk data |
| ECDSA P-256 | No | Yes | 128-bit | Fast signatures; standard TLS certs |
| ECDH / ECDHE | Yes | No | 128-bit | Perfect forward secrecy in TLS 1.3 |
| DH / DHE | Yes | No | 128-bit (3072-bit key) | Replaced by ECDHE in modern TLS |
| Ed25519 | No | Yes | ~128-bit | SSH keys, modern PKI |
What to study next
Got this wrong? Here's your next step.
Review block sizes, usable host formulas (2^n − 2), and how to find network and broadcast addresses for /24 through /30. Then practise related PCNE subnetting questions on CIDR, address ranges, and subnet selection.
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FAQ
Questions learners often ask
What does this PCNE question test?
Managing, Monitoring, and Optimising Network Operations — This question tests Managing, Monitoring, and Optimising Network Operations — CIDR notation defines the prefix length..
What is the correct answer to this question?
The correct answer is: Both VPCs have a default route (0.0.0.0/0) pointing to different next hops — VPC peering does not enforce symmetric routing by default. If both networks have subnet CIDRs that overlap, or if one network has a route that sends traffic to the other via a different next hop (e.g., VPN or NAT), asymmetric routing can occur. The most common cause is when both VPCs have a default route pointing to different next hops (e.g., one to the internet, one to a VPN), causing different paths.
What should I do if I get this PCNE question wrong?
Review block sizes, usable host formulas (2^n − 2), and how to find network and broadcast addresses for /24 through /30. Then practise related PCNE subnetting questions on CIDR, address ranges, and subnet selection.
What is the key concept behind this question?
CIDR notation defines the prefix length.
About these practice questions
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Last reviewed: Jul 4, 2026
This PCNE practice question is part of Courseiva's free Google Cloud certification practice question bank. Courseiva provides original exam-style practice questions with explanations, topic-based practice, mock exams, readiness tracking, and study analytics to help learners prepare for the PCNE exam.
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