PCNE Configuring Network Services Practice Question
A company has deployed an external HTTPS load balancer with a Cloud CDN backend. The load balancer uses a managed SSL certificate. Recently, the company updated their DNS record to point to a different IP address of a new load balancer. After the change, some users are still being served from the old load balancer's cache. The network engineer has confirmed that the DNS TTL has expired. What is the most likely cause of this issue?
⚠ Common exam trap
Google Cloud often tests the distinction between DNS TTL (which controls how long DNS records are cached by resolvers) and HTTP cache TTL (which controls how long content is cached by CDN edge nodes), leading candidates to incorrectly attribute the issue to DNS propagation rather than CDN cache expiration.
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
✓
Cloud CDN cached responses from the old load balancer may still be served until their cache TTL expires.
Cloud CDN caches content at Google's edge caches based on the cache-control headers or default cache TTL. When the DNS record is updated to point to a new load balancer, the old load balancer's cached responses may still be served from edge caches until their cache TTL expires, even after the DNS TTL has expired. This is because Cloud CDN caches are independent of DNS resolution and are governed by HTTP caching rules.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
Cloud CDN cached responses from the old load balancer may still be served until their cache TTL expires.
Why this is correct
Cloud CDN caches content at edge locations; if the cache TTL has not expired, users may receive the old content even after DNS changes.
- ✗
The old load balancer's SSL certificate is still cached by clients.
Why it's wrong here
SSL certificates are not cached at client-side; the browser receives the new certificate from the new load balancer.
- ✗
The DNS change has not propagated globally despite the TTL expiring.
Why it's wrong here
The engineer confirmed the TTL has expired, so DNS should be updated globally.
- ✗
The old load balancer's IP address is still being served by Google's edge network due to anycast.
Why it's wrong here
Anycast ensures that the DNS change points to the new IP; the old IP is no longer advertised.
Visual reference
Go deeper
Related to this question
About these practice questions
One of 961 original PCNE practice questions on Courseiva, each with a full explanation and wrong-answer analysis — not exam dumps or protected exam content. Learn why practice questions differ from exam dumps →
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.