- A
PAT translates multiple internal addresses to a single public IP address by using unique source port numbers.
PAT distinguishes between multiple internal hosts sharing the same public IP by assigning a different source port for each session. The router maintains a translation table that tracks the original internal IP and port along with the assigned public IP and port.
- B
PAT requires a 1:1 mapping of internal to external IP addresses.
Why wrong: PAT does not require a 1:1 mapping; it allows many internal addresses to share a single public IP. A 1:1 mapping is characteristic of static NAT, not PAT.
- C
PAT can only be configured with a pool of public IP addresses.
Why wrong: PAT can be configured with either a single public IP address (using the interface address) or a pool of public IP addresses. It does not require a pool; a single address is sufficient for PAT overload.
- D
PAT uses both IP addresses and port numbers to track translations.
PAT extends NAT by using the transport layer port numbers (e.g., TCP/UDP ports) along with IP addresses to uniquely identify each translation. This allows multiple internal hosts to share the same public IP.
- E
PAT translations are always static and never time out.
Why wrong: PAT translations are dynamic and have a timeout (default 86400 seconds for general translations, but shorter for TCP/UDP). They are removed after the session ends or the timeout expires.
Quick Answer
The correct answer is that PAT uses both IP addresses and port numbers to track translations, enabling many internal hosts to share a single public IP. This works because PAT assigns a unique source port number to each outbound session, creating a many-to-one mapping that the router uses to demultiplex return traffic back to the correct internal host. On the CCNA 200-301 v2 exam, this concept tests your understanding of how NAT overload differs from static NAT and dynamic NAT without a pool; a common trap is confusing PAT’s many-to-one behavior with the 1:1 mapping of static NAT. Remember that PAT conserves public IPs by leveraging the port number as an identifier, so think of it as “many hosts, one IP, many ports.” A helpful memory tip is “PAT = Port Address Translation, so it’s all about the port.”
CCNA Network Services and Security Practice Question
This 200-301 practice question tests your understanding of network services and security. This is a configuration task: choose the command set that satisfies every stated requirement. Small differences — like 'secret' vs 'password' or 'transport input ssh' vs 'all' — change whether the answer is correct. 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.
Which TWO statements correctly describe the behavior of PAT (Port Address Translation) as configured on a Cisco router?
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
PAT translates multiple internal addresses to a single public IP address by using unique source port numbers.
PAT (Port Address Translation) translates multiple internal private IP addresses to a single public IP address by assigning unique source port numbers to each session, allowing many internal hosts to share one public IP. This is correctly described in option A. Option D is also correct because PAT uniquely identifies each translation by both the IP address and the port number, enabling the router to demultiplex return traffic. Option B is wrong because PAT uses many-to-one mapping, not 1:1; a 1:1 mapping is characteristic of static NAT. Option C is incorrect because PAT can operate with a single public IP address (often the outside interface address) rather than requiring a pool. Option E is false because PAT translations are dynamically created and time out after a period of inactivity; they are not static.
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.
- ✓
PAT translates multiple internal addresses to a single public IP address by using unique source port numbers.
Why this is correct
PAT distinguishes between multiple internal hosts sharing the same public IP by assigning a different source port for each session. The router maintains a translation table that tracks the original internal IP and port along with the assigned public IP and port.
Related concept
Read the scenario before looking for a memorised answer.
- ✗
PAT requires a 1:1 mapping of internal to external IP addresses.
- ✗
PAT can only be configured with a pool of public IP addresses.
Why it's wrong here
PAT can be configured with either a single public IP address (using the interface address) or a pool of public IP addresses. It does not require a pool; a single address is sufficient for PAT overload.
- ✓
PAT uses both IP addresses and port numbers to track translations.
- ✗
PAT translations are always static and never time out.
Option-by-option analysis
Why each answer is right or wrong
Understanding why wrong answers are wrong — and when they would be correct — is what separates a 750 score from a 900. The 200-301 exam frequently reuses these exact scenarios with slightly different constraints.
✓PAT translates multiple internal addresses to a single public IP address by using unique source port numbers.Correct answer▾
Why this is correct
PAT distinguishes between multiple internal hosts sharing the same public IP by assigning a different source port for each session. The router maintains a translation table that tracks the original internal IP and port along with the assigned public IP and port.
✗PAT requires a 1:1 mapping of internal to external IP addresses.Wrong answer — click to see why▾
Why this is wrong here
PAT does not require a 1:1 mapping; it allows many internal addresses to share a single public IP. A 1:1 mapping is characteristic of static NAT, not PAT.
Why candidates choose this
Students often confuse PAT with static NAT, thinking that each internal host needs its own public IP. They may also misinterpret 'translation' as requiring a one-to-one correspondence.
✗PAT can only be configured with a pool of public IP addresses.Wrong answer — click to see why▾
Why this is wrong here
PAT can be configured with either a single public IP address (using the interface address) or a pool of public IP addresses. It does not require a pool; a single address is sufficient for PAT overload.
Why candidates choose this
Some students believe that PAT, like dynamic NAT, requires a pool of addresses. They may not realize that PAT can overload a single address by using port numbers.
✗PAT translations are always static and never time out.Wrong answer — click to see why▾
Why this is wrong here
PAT translations are dynamic and have a timeout (default 86400 seconds for general translations, but shorter for TCP/UDP). They are removed after the session ends or the timeout expires.
Why candidates choose this
Students may think that all NAT translations are static because they hear about 'static NAT' or confuse PAT with static entries. They might also assume that translations persist indefinitely.
Analysis generated from the official 200-301blueprint and verified against question context. The “when correct” sections are what AI assistants cite when candidates ask “what’s the difference between these options?”
Common exam traps
Common exam trap: answer the scenario, not the keyword
Cisco often tests the misconception that PAT requires a pool of public IPs or a 1:1 mapping, when in fact PAT is designed for many-to-one translation using port numbers, and can operate with a single public IP address.
Detailed technical explanation
How to think about this question
PAT, also known as NAT overload, modifies the source port number in the TCP/UDP header to a unique value (typically above 1024) and stores the mapping in the NAT translation table. This allows up to 65,536 simultaneous sessions per public IP (theoretically, limited by port range and memory). In real-world scenarios, PAT is commonly used in home routers and enterprise edge devices to conserve public IPv4 addresses, and it works seamlessly with most applications except those that embed IP addresses in the payload (e.g., FTP active mode or SIP).
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
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FAQ
Questions learners often ask
What does this 200-301 question test?
Network Services and Security — This question tests Network Services and Security — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: PAT translates multiple internal addresses to a single public IP address by using unique source port numbers. — PAT (Port Address Translation) translates multiple internal private IP addresses to a single public IP address by assigning unique source port numbers to each session, allowing many internal hosts to share one public IP. This is correctly described in option A. Option D is also correct because PAT uniquely identifies each translation by both the IP address and the port number, enabling the router to demultiplex return traffic. Option B is wrong because PAT uses many-to-one mapping, not 1:1; a 1:1 mapping is characteristic of static NAT. Option C is incorrect because PAT can operate with a single public IP address (often the outside interface address) rather than requiring a pool. Option E is false because PAT translations are dynamically created and time out after a period of inactivity; they are not static.
What should I do if I get this 200-301 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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Last reviewed: Jun 11, 2026
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