This 300-410 practice question tests your understanding of nat and pat. 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 network engineer runs the following command to troubleshoot PAT exhaustion:
[Id: 1] access-list NAT permit ip 10.0.0.0 0.255.255.255 any
refcount 1024, pool MyPool
pool MyPool: netmask 255.255.255.240
start 203.0.113.1 end 203.0.113.14
type generic, total addresses 14, allocated 14 (100%), misses 0
What is the most likely issue?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue: "most likely"
Why it matters: Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
The pool is exhausted; PAT is using all addresses, but port exhaustion may occur.
The pool has only 14 addresses, and all are allocated (100%). With 1024 active translations, this indicates PAT is using all addresses and may be running out of ports.
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 pool is exhausted; PAT is using all addresses, but port exhaustion may occur.
Why this is correct
All 14 addresses are allocated, meaning PAT is using them, but with 1024 translations, ports may be running out.
Clue confirmation
The clue word "most likely" in the question point toward this answer.
The access list is misconfigured, blocking traffic.
Why it's wrong here
The access list is correct; it matches the inside network.
✗
The outside interface is down.
Why it's wrong here
No indication of interface issues.
✗
Static translations are missing.
Why it's wrong here
Static translations are not needed here.
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.
Related glossary terms
Concepts from this question explained
These glossary pages explain the core terms tested in this 300-410 question in full detail.
Review block sizes, usable host formulas (2^n − 2), and how to find network and broadcast addresses for /24 through /30. Then practise related 300-410 subnetting questions on CIDR, address ranges, and subnet selection.
NAT and PAT — This question tests NAT and PAT — CIDR notation defines the prefix length..
What is the correct answer to this question?
The correct answer is: The pool is exhausted; PAT is using all addresses, but port exhaustion may occur. — The pool has only 14 addresses, and all are allocated (100%). With 1024 active translations, this indicates PAT is using all addresses and may be running out of ports.
What should I do if I get this 300-410 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 300-410 subnetting questions on CIDR, address ranges, and subnet selection.
Are there clue words in this question I should notice?
Yes — watch for: "most likely". Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
What is the key concept behind this question?
CIDR notation defines the prefix length.
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