Quick Answer
The answer is 300 seconds, or five minutes, as the recommended default UDP NAT timeout per RFC 4787. This standard, titled "Network Address Translation (NAT) Behavioral Requirements for UDP," establishes that a UDP mapping should remain active for at least five minutes after the last packet is seen to balance application responsiveness with efficient port utilization. On the Cisco CCNP ENARSI 300-410 exam, this concept tests your understanding of NAT stateful behavior and the difference between UDP and TCP timeouts—a common trap is confusing the UDP default with TCP's longer default or assuming the timeout is indefinite. Cisco IOS routers honor this RFC by default, so you may see show ip nat translations output reflecting entries aged at 300 seconds. For a quick memory tip, think "UDP is quick, so five minutes is thick"—the short, connectionless nature of UDP still needs a generous timeout to handle DNS and VoIP traffic without premature drops.
This 300-410 practice question tests your understanding of nat and pat. 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.
According to RFC 4787 (NAT Behavioral Requirements for UDP), what is the recommended default timeout for UDP NAT mappings?
60 seconds
Why wrong: This is too short for general UDP traffic; RFC 4787 recommends 5 minutes.
300 seconds
Correct. RFC 4787 recommends and Cisco IOS defaults to 300 seconds for UDP NAT mappings.
600 seconds
Why wrong: This is not the recommended default; 300 seconds is the standard.
86400 seconds
Why wrong: This is the default for basic NAT, not UDP mappings.
Answer choices
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
300 seconds
RFC 4787 recommends a default UDP mapping timeout of 5 minutes (300 seconds). Cisco IOS defaults to this value for UDP NAT translations.
Key principle: NAT direction and interface roles matter as much as the IP address mapping. Inside/outside designation controls which traffic is translated.
Answer analysis
For each option: why learners choose it and why it is or isn't the right answer here.
60 seconds
Why it's wrong here
This is too short for general UDP traffic; RFC 4787 recommends 5 minutes.
300 seconds
600 seconds
Why it's wrong here
This is not the recommended default; 300 seconds is the standard.
86400 seconds
Common exam traps
NAT is not only about the public address. The inside/outside interface roles and the ACL or rule that matches traffic are just as important.
Detailed technical explanation
NAT questions usually test address translation, overload/PAT behaviour, static mappings and whether the right traffic is being translated. Read the interface direction and address terms carefully.
Key takeaway
NAT direction and interface roles matter as much as the IP address mapping. Inside/outside designation controls which traffic is translated.
Real-world example
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
Review the four NAT address types (inside local, inside global, outside local, outside global), PAT port overload, and static vs dynamic NAT use cases. Then practise related 300-410 NAT questions on configuration and troubleshooting.
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FAQ
NAT and PAT — This question tests NAT and PAT — Static NAT maps one inside address to one outside address..
The correct answer is: 300 seconds — RFC 4787 recommends a default UDP mapping timeout of 5 minutes (300 seconds). Cisco IOS defaults to this value for UDP NAT translations.
Review the four NAT address types (inside local, inside global, outside local, outside global), PAT port overload, and static vs dynamic NAT use cases. Then practise related 300-410 NAT questions on configuration and troubleshooting.
Static NAT maps one inside address to one outside address.
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Last reviewed: Jun 19, 2026
This 300-410 practice question is part of Courseiva's free Cisco certification practice question bank. Courseiva provides original exam-style practice questions with explanations, topic-based practice, mock exams, readiness tracking, and study analytics to help learners prepare for the 300-410 exam.
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