PCNE Practice Question: Managing, Monitoring, and Optimising Network Operations
A company has two VPCs connected via VPC Network Peering. Traffic from an instance in VPC A to an instance in VPC B is failing. Connectivity Tests show that the expected route exists and firewall rules allow the traffic. What is a possible 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
✓
Asymmetric routing due to conflicting routes
Asymmetric routing can occur when a packet goes from A to B via peering, but the return packet takes a different path (e.g., through a VPN) due to route priorities. This can result in dropped packets.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
VPC Flow Logs are disabled
Why it's wrong here
Flow Logs do not affect traffic; they only log it.
- ✗
The MTU of the instances is set to 1500
Why it's wrong here
GCP supports 1460-byte MTU, but this is unlikely the issue.
- ✗
The VPC peering is not in active state
Why it's wrong here
Connectivity Tests would likely detect this.
- ✓
Asymmetric routing due to conflicting routes
Why this is correct
Asymmetric routing can break connections if the return path is different.
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 |
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JA
Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
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.