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300-410 Practice Question: Which THREE symptoms indicate that NAT is…
Which THREE symptoms indicate that NAT is misconfigured or failing on a Cisco router? (Choose THREE.)
⚠ Common exam trap
Cisco often tests the distinction between connectivity to the outside interface (which does not require NAT) and connectivity beyond it (which requires proper NAT translation), leading candidates to mistakenly think that successful pings to the outside interface imply full NAT functionality.
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
✓
Inside hosts can ping the outside interface IP but cannot reach hosts beyond it.
If inside hosts can ping the outside interface IP but cannot reach hosts beyond it, this indicates that NAT is translating the source address correctly for outbound traffic, but the router is not performing NAT for destinations beyond the outside interface. This typically happens when the NAT configuration lacks an access list that matches the inside-to-outside traffic or when the ip nat inside/outside interface commands are misapplied, causing the router to forward packets without translation for destinations beyond the directly connected network.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
Inside hosts can ping the outside interface IP but cannot reach hosts beyond it.
Why this is correct
This often indicates that NAT is not translating the source address for packets going out, or the return traffic is not being untranslated.
- ✓
Traffic flows in one direction only (e.g., inside-to-outside works, but return traffic fails).
Why this is correct
Asymmetric routing or missing NAT entries can cause one-way traffic; the router may not have a translation for the return packet.
- ✓
The show ip nat translations output shows many translations with the same inside global address but different ports, and new connections fail.
Why this is correct
This indicates PAT port exhaustion; when all available ports are used, new translations cannot be created.
- ✗
The router's CPU utilization is high due to BGP process.
Why it's wrong here
High CPU from BGP is unrelated to NAT; NAT issues typically do not cause high CPU unless there is a bug or extremely high traffic.
- ✗
The show ip route command shows a default route pointing to the ISP next hop.
Why it's wrong here
A default route is normal for internet access and does not indicate a NAT problem.
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Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
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