Exam Professional Cloud Network Engineer topic 1 question 171 discussion

D, as explained in https://cloud.google.com/network-intelligence-center/docs/performance-dashboard/concepts/metrics-views?hl=en#metric_availability_and_confidence_levels and https://cloud.google.com/network-intelligence-center/docs/performance-dashboard/concepts/metrics-views?hl=en#packet-loss "90% confidence 2.5 VMs multiplied by the number of zones in the project." Which in our case is 2.5 x 4 = 10. "If the peered networks are in different projects, packet loss is visible in the destination project." Which in this case is project B.

D only

For a 90% confidence, the required number of VMs in each zone is 2.5 VMs x the number of zones in the project, so 10 VMs per zone. Packet loss is visible in the destination project.

https://cloud.google.com/vpc/docs/monitoring-packet-mirroring

If it's 2.5 x 4 zones wouldn't that be 10? 2.25 x 4 zones equals 9 which is not what the link states. Are you factoring in the 90% to get to 9?

90% confidence 2.5 VMs x the number of zones in the project. For example, if you have 12 zones in your project, you must have 30 VMs in each zone.

Anything with VPC A as the destination is wrong: On the other hand, suppose that these two networks are not in the same project. That is, suppose network A is part of project A, and network M is part of project M. When the networks are peered, project M's Performance Dashboard shows packet loss data for situations where zone M is the destination zone. Conversely, when zone A is the destination zone, the packet loss data is visible only to project A

To achieve a reported packet loss metric with at least a 90% confidence level, you need to ensure that the sample size is adequate for statistical significance. In this case, the question mentions that the packet loss investigation is for traffic flows starting in VPC A and terminating in VPC B. Since the traffic is originating from VPC A and terminating in VPC B, you should look in Project B for the reported metric, as this is where the traffic terminates. This makes options A and C incorrect. Now, you need to ensure that each zone in each of the VPC networks has at least 9 compute instances to provide a sufficient sample size for statistical analysis with a 90% confidence level. Therefore, the correct answer is: B. Ensure that each zone in each of the VPC networks has at least 9 compute instances. Look in Project B for the reported metric.

"The metrics for the collector destination provides an aggregate view of all mirrored traffic that it collects. However, for the individual mirrored instances, you can view the number of mirrored packets that were dropped. Metrics for the collector destination don't include dropped packets." https://cloud.google.com/vpc/docs/monitoring-packet-mirroring