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300-410 Practice Question: Is a limitation of NAT as defined in RFC 2663?
Which of the following is a limitation of NAT as defined in RFC 2663?
⚠ Common exam trap
Cisco often tests the misconception that NAT is transparent to all traffic, when in fact it breaks end-to-end connectivity and requires ALGs for protocols that embed addressing information in the payload.
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
✓
NAT breaks end-to-end IP connectivity and can interfere with application-layer protocols.
RFC 2663 defines NAT as a mechanism that modifies IP addresses and/or ports in packet headers, which inherently breaks the end-to-end IP connectivity model. This modification can interfere with application-layer protocols that embed IP addresses or port numbers in their payload, such as FTP, SIP, or DNS, because NAT does not automatically translate these embedded addresses.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
NAT cannot translate UDP traffic.
Why it's wrong here
NAT can translate UDP traffic using PAT.
- ✗
NAT is incompatible with TCP traffic.
Why it's wrong here
NAT works with TCP traffic.
- ✓
NAT breaks end-to-end IP connectivity and can interfere with application-layer protocols.
Why this is correct
Correct. This is a well-known limitation of NAT as per RFC 2663.
- ✗
NAT requires all traffic to be encrypted.
Why it's wrong here
NAT does not require encryption.
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JA
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.