- A
Verify BGP timers (keepalive/hold) match on both sides
Mismatched timers cause session flaps.
- B
Review the BGP route advertisements for policy conflicts
Routing policy conflicts can cause the session to reset.
- C
Disable ECMP on Cloud Router
Why wrong: ECMP does not cause BGP flaps.
- D
Check the MTU on the on-premises router
MTU mismatch can cause BGP session drops.
- E
Enable VPC Flow Logs on the interconnect subnet
Why wrong: VPC Flow Logs show traffic flows but not BGP session details.
Question 870 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. The scenario asks you to isolate a root cause — eliminate options that address a different problem before choosing. 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 is using Cloud Router with BGP for connectivity to an on-premises network via Partner Interconnect. The BGP session is flapping. Which THREE actions should the engineer take to diagnose the issue?
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
✓
Verify BGP timers (keepalive/hold) match on both sides
Common causes of BGP flaps include MTU mismatch, misconfigured timers, or routing policy issues. Checking MTU, BGP timers, and route advertisements helps identify the root cause.
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.
- ✓
Verify BGP timers (keepalive/hold) match on both sides
Why this is correct
Mismatched timers cause session flaps.
Related concept
CIDR notation defines the prefix length.
- ✓
Review the BGP route advertisements for policy conflicts
Why this is correct
Routing policy conflicts can cause the session to reset.
Related concept
CIDR notation defines the prefix length.
- ✗
Disable ECMP on Cloud Router
Why it's wrong here
ECMP does not cause BGP flaps.
- ✓
Check the MTU on the on-premises router
- ✗
Enable VPC Flow Logs on the interconnect subnet
Why it's wrong here
VPC Flow Logs show traffic flows but not BGP session details.
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.
Trap categories for this question
Command / output trap
VPC Flow Logs show traffic flows but not BGP session details.
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.
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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Managing, Monitoring, and Optimising Network Operations — study guide chapter
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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: Verify BGP timers (keepalive/hold) match on both sides — Common causes of BGP flaps include MTU mismatch, misconfigured timers, or routing policy issues. Checking MTU, BGP timers, and route advertisements helps identify the root cause.
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.
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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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