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300-410 Practice Question: Is true regarding the default behavior of NAT in…
Which of the following is true regarding the default behavior of NAT in Cisco IOS when handling ICMP traffic?
⚠ Common exam trap
Cisco often tests the misconception that ICMP NAT entries are permanent or use the same timeout as TCP, when in fact they have a distinct and much shorter default timeout of 60 seconds.
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
✓
ICMP NAT entries timeout after 60 seconds by default.
C is correct because Cisco IOS NAT uses a default timeout of 60 seconds for ICMP NAT entries. When an ICMP packet is translated, the router creates a NAT translation entry, and if no subsequent traffic matches that entry within 60 seconds, the entry is removed. This behavior is independent of TCP or UDP timeouts and is specific to ICMP.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
ICMP traffic is not translated by NAT unless explicitly configured.
Why it's wrong here
Cisco IOS NAT translates ICMP traffic by default.
- ✗
ICMP NAT entries use the same timeout as TCP entries by default.
Why it's wrong here
ICMP NAT entries have a default timeout of 60 seconds, not 86400.
- ✓
ICMP NAT entries timeout after 60 seconds by default.
Why this is correct
Correct. The default timeout for ICMP NAT entries is 60 seconds in Cisco IOS.
- ✗
ICMP NAT entries are permanent and do not time out.
Why it's wrong here
ICMP NAT entries are dynamic and time out after 60 seconds.
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Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
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.