The correct answer is that the filter XPath is too broad and may cause excessive CPU usage on frequent changes. This occurs because the on-change telemetry subscription with the XPath /interfaces/interface/state monitors all interface state data, meaning any operational change—such as link flaps, speed negotiation, or counters updating—triggers a push notification, overwhelming the device’s CPU with constant encoding and transmission. On the ENCOR 350-401 exam, this scenario tests your understanding of how broad XPath filters in on-change subscriptions can lead to performance degradation, a common trap where students focus only on syntax correctness rather than operational impact. A key memory tip is to think of “broad XPath” as a “CPU hog”—always narrow your filter to specific leaf nodes or subtrees when using on-change update policies to avoid flooding the control plane.
CCNP Model-Driven Telemetry Practice Question
This 350-401 practice question tests your understanding of model-driven telemetry. 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.
Consider the following telemetry configuration on a Cisco IOS-XE device:
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
The filter XPath is too broad and may cause excessive CPU usage on frequent changes.
On-change subscriptions can generate high CPU load if the monitored data changes frequently, which may impact device performance.
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 on-change policy will not work without a periodic fallback.
Why it's wrong here
On-change works independently; a periodic fallback is optional but not required.
✓
The filter XPath is too broad and may cause excessive CPU usage on frequent changes.
Why this is correct
A broad filter like /interfaces/interface/state can cause high CPU if many interfaces change state often.
The receiver IP address must be on the same subnet as the device.
Why it's wrong here
The receiver can be anywhere reachable via IP routing.
✗
The encoding should be encode-xml for on-change subscriptions.
Why it's wrong here
encode-kvgpb is valid for any update policy.
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 small business has 20 workstations on the 192.168.1.0/24 network and one public IP from its ISP. The router uses PAT (NAT overload) so all 20 devices share one public address using different source ports. NAT questions test whether you understand the four address terms and which direction each translation applies.
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 350-401 subnetting questions on CIDR, address ranges, and subnet selection.
Model-Driven Telemetry — This question tests Model-Driven Telemetry — CIDR notation defines the prefix length..
What is the correct answer to this question?
The correct answer is: The filter XPath is too broad and may cause excessive CPU usage on frequent changes. — On-change subscriptions can generate high CPU load if the monitored data changes frequently, which may impact device performance.
What should I do if I get this 350-401 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 350-401 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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Question Discussion
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