This 200-901 practice question tests your understanding of network fundamentals. Read the scenario carefully and evaluate each option against the stated constraints before committing to an answer. 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.
Exhibit
R1# show ip nat translations
Pro Inside global Inside local Outside local Outside global
icmp 203.0.113.10:1 10.0.0.1:1 192.0.2.5:1 192.0.2.5:1
tcp 203.0.113.10:80 10.0.0.1:80 192.0.2.5:80 192.0.2.5:80
Based on the NAT translation table, what type of NAT is being used?
R1# show ip nat translations
Pro Inside global Inside local Outside local Outside global
icmp 203.0.113.10:1 10.0.0.1:1 192.0.2.5:1 192.0.2.5:1
tcp 203.0.113.10:80 10.0.0.1:80 192.0.2.5:80 192.0.2.5:80
A
Dynamic NAT
Why wrong: Dynamic NAT assigns a different global address for each session, but here only one global address is used.
B
Static PAT
Why wrong: Static PAT is a one-to-one mapping of a specific port, but the translations show multiple ports for the same global IP.
C
Static NAT
Why wrong: Static NAT maps one inside local to one inside global, but here multiple local addresses use the same global address.
D
PAT (overload)
PAT uses port numbers to distinguish between multiple internal hosts sharing a single public IP.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
PAT (overload)
The NAT translation table shows multiple internal IP addresses (e.g., 10.1.1.1, 10.1.1.2) being translated to the same public IP address (e.g., 203.0.113.1) but with different source ports. This is the defining characteristic of Port Address Translation (PAT), also known as NAT overload, where a single public IP is shared among many internal hosts by multiplexing on layer-4 port numbers.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
✗
Dynamic NAT
Why it's wrong here
Dynamic NAT assigns a different global address for each session, but here only one global address is used.
✗
Static PAT
Why it's wrong here
Static PAT is a one-to-one mapping of a specific port, but the translations show multiple ports for the same global IP.
✗
Static NAT
Why it's wrong here
Static NAT maps one inside local to one inside global, but here multiple local addresses use the same global address.
✓
PAT (overload)
Why this is correct
PAT uses port numbers to distinguish between multiple internal hosts sharing a single public IP.
Related concept
Read the scenario before looking for a memorised answer.
Common exam traps
Common exam trap: answer the scenario, not the keyword
Cisco often tests the distinction between Dynamic NAT (which uses a pool of public IPs) and PAT (which overloads a single public IP with port numbers), and the trap here is that candidates see multiple translations and assume Dynamic NAT, missing the key clue that the public IP is identical across entries.
Trap categories for this question
Command / output trap
Static PAT is a one-to-one mapping of a specific port, but the translations show multiple ports for the same global IP.
Detailed technical explanation
How to think about this question
PAT works by modifying the source port in the TCP/UDP header to a unique value (typically above 1024) and maintaining a translation table that tracks the original (private IP:port) to (public IP:assigned port) mapping. This allows up to ~65,536 simultaneous sessions per public IP (limited by port range and available memory). In real-world deployments, PAT is essential for conserving public IPv4 addresses, especially in home and small office routers using RFC 1918 private addresses.
KKey Concepts to Remember
Read the scenario before looking for a memorised answer.
Find the constraint that changes the correct option.
Eliminate answers that are true in general but not in this case.
TExam Day Tips
→Watch for words such as best, first, most likely and least administrative effort.
→Review why wrong options are wrong, not only why the correct option is correct.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
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.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Network Fundamentals — This question tests Network Fundamentals — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: PAT (overload) — The NAT translation table shows multiple internal IP addresses (e.g., 10.1.1.1, 10.1.1.2) being translated to the same public IP address (e.g., 203.0.113.1) but with different source ports. This is the defining characteristic of Port Address Translation (PAT), also known as NAT overload, where a single public IP is shared among many internal hosts by multiplexing on layer-4 port numbers.
What should I do if I get this 200-901 question wrong?
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
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