CCNA Network Services and Security Practice Question
Exhibit
Current NAT: ip nat inside source list 10 interface GigabitEthernet0/0 overload
A branch office uses PAT overload on the edge router. Inside users can reach the internet, but return traffic for a newly deployed server must be mapped to a specific inside host. Which two statements are correct?
⚠ Common exam trap
A frequent exam trap is assuming that PAT overload can handle inbound connections to a specific inside host because it manages many-to-one address sharing. However, PAT overload dynamically assigns ports for outbound sessions and does not reserve a fixed public IP and port combination for inbound traffic. This misconception leads to incorrect answers suggesting dynamic NAT or PAT overload can support inbound server access without additional configuration. The key is recognizing that only static NAT provides a consistent public-to-private mapping necessary for inbound connectivity to a server.
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
✓
A static NAT entry can provide a consistent public-to-private mapping for the server
PAT overload is great for many inside clients sharing a public IP for outbound sessions. A public-facing server that needs predictable inbound reachability typically requires static NAT or static PAT.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
A static NAT entry can provide a consistent public-to-private mapping for the server
Why this is correct
Static NAT creates a fixed one-to-one translation between a specific inside private IP and a specific outside public IP. This guarantees that inbound connections from the internet, such as those to a web or mail server, are always sent to the correct internal host regardless of session timing. Unlike dynamic NAT or PAT, the mapping is constant, which is why it is required for reliable inbound access to a server.
- ✓
PAT overload is designed mainly for many-to-one outbound address sharing
Why this is correct
PAT overload multiplexes many private inside addresses onto a single public outside address by assigning each session a unique source port number. It is optimized for outbound traffic where the router maintains state of the connection tuple, translating source IP and port, and then reversing the translation for return traffic. This design efficiently conserves public IPv4 addresses, making it the standard for branch offices that need shared internet access.
- ✗
Dynamic NAT always supports inbound access without additional configuration
Why it's wrong here
Dynamic NAT assigns public addresses from a pool only while sessions are active, meaning the mapping changes over time and is not predictable for inbound connections. Incoming packets from the internet require a known, stable destination, but dynamic NAT provides no guaranteed association between a given public IP and an internal host. Therefore additional configuration, such as static NAT or port forwarding, is always required to support incoming traffic.
When this WOULD be correct
In a scenario where a network uses dynamic NAT with a pool of public IPs and an inside host initiates outbound traffic, the return traffic is automatically allowed due to the stateful nature of NAT, so dynamic NAT can support inbound access for responses to outbound sessions without extra config.
- ✗
NAT is unrelated to whether private addresses can reach the public internet
Why it's wrong here
The statement is false because NAT/PAT is exactly the mechanism that lets RFC 1918 private addresses communicate with the public internet. Without NAT, public routers would have no route for replies destined to a private address, so the return traffic would be dropped. Thus, private address reachability to the internet is fundamentally dependent on NAT/PAT at the edge, not unrelated to it.
When this WOULD be correct
This option would be correct in a question about the relationship between NAT and internet reachability for public IP addresses. For example: 'A host with a public IP address does not require NAT to reach the public internet.'
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.
✓A static NAT entry can provide a consistent public-to-private mapping for the serverCorrect answer▾
Why this is correct
Static NAT creates a fixed one-to-one translation between a specific inside private IP and a specific outside public IP. This guarantees that inbound connections from the internet, such as those to a web or mail server, are always sent to the correct internal host regardless of session timing. Unlike dynamic NAT or PAT, the mapping is constant, which is why it is required for reliable inbound access to a server.
✗Dynamic NAT always supports inbound access without additional configurationWrong answer — click to see why▾
Why this is wrong here
Dynamic NAT does not support inbound access without additional configuration because it requires a pool of public addresses and does not automatically map inbound traffic to a specific inside host without manual static entries.
★ When this WOULD be the correct answer
In a scenario where a network uses dynamic NAT with a pool of public IPs and an inside host initiates outbound traffic, the return traffic is automatically allowed due to the stateful nature of NAT, so dynamic NAT can support inbound access for responses to outbound sessions without extra config.
Why candidates choose this
Candidates may confuse dynamic NAT with PAT or assume that NAT inherently allows inbound traffic, overlooking that dynamic NAT only creates mappings for outbound-initiated sessions and does not provide fixed inbound mappings.
✗NAT is unrelated to whether private addresses can reach the public internetWrong answer — click to see why▾
Why this is wrong here
NAT is directly related to whether private addresses can reach the public internet; without NAT (or a proxy), private IP addresses are not routable on the public internet, so this statement is false.
★ When this WOULD be the correct answer
This option would be correct in a question about the relationship between NAT and internet reachability for public IP addresses. For example: 'A host with a public IP address does not require NAT to reach the public internet.'
Why candidates choose this
Candidates may confuse the role of NAT with other technologies like routing or firewalls, or they may think that private addresses can reach the internet without address translation if a default route exists.
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?”
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Key term
Router
A router is a networking device that connects different networks together and directs data traffic between them by choosing the best path for data to travel.
Key term
NAT
NAT (Network Address Translation) is a method that allows multiple devices on a private network to share a single public IP address when accessing the internet.
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JA
Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
This 200-301 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 200-301 exam.