Question 1hardmultiple choice
Full question →hardmultiple choiceObjective-mapped
A company wants internal users to share one public IPv4 address for outbound Internet access, while keeping sessions separate. Which NAT approach best meets that requirement?
Answer choices
Why each option matters
Good practice is not just finding the correct option. The wrong answers often show the exact trap the exam wants you to fall into.
A
Best answer
PAT overload
This is correct because PAT uses port values to let many internal sessions share one public IPv4 address.
B
Distractor review
Static NAT only
This is wrong because static NAT is a one-to-one approach, not the many-to-one sharing model described.
C
Distractor review
No NAT, because private IPv4 addresses are Internet-routable
This is wrong because private IPv4 addresses are not routed on the public Internet.
D
Distractor review
DHCP relay
This is wrong because DHCP relay is unrelated to public address translation.
Common exam trap
Common exam trap: answer the scenario, not the keyword
A common exam trap is selecting static NAT as the solution because it involves address translation, but static NAT only supports one-to-one mappings and cannot handle multiple internal users sharing a single public IP address. Another frequent mistake is assuming private IPv4 addresses can be routed on the Internet without NAT, which is incorrect because private addresses are non-routable externally. Additionally, confusing DHCP relay with NAT functions can mislead candidates, as DHCP relay only forwards DHCP messages and does not perform address translation. Recognizing that PAT overload uniquely enables many-to-one translation with port differentiation is crucial to avoid these pitfalls.
Technical deep dive
How to think about this question
Network Address Translation (NAT) is a fundamental IP service that modifies IP address information in packet headers while in transit, enabling private IP networks to communicate with public networks. The core concept behind NAT is to conserve public IPv4 addresses by allowing multiple devices on a private network to share a limited number of public IP addresses. Port Address Translation (PAT), also known as NAT overload, extends this by using unique source port numbers to distinguish multiple sessions from different internal hosts sharing a single public IP address. In the CCNA context, PAT overload is the preferred NAT method when many internal users need simultaneous outbound Internet access but only one public IPv4 address is available. PAT translates multiple private IP addresses to a single public IP address by assigning unique source port numbers to each session, ensuring that return traffic is correctly routed back to the originating internal host. This many-to-one translation model contrasts with static NAT, which maps one private IP to one public IP, and dynamic NAT, which requires a pool of public IP addresses. A common exam trap is confusing static NAT with PAT overload. Static NAT provides a fixed one-to-one mapping and cannot support multiple internal users sharing a single public IP address simultaneously. Additionally, some may mistakenly believe that private IP addresses are routable on the Internet or that DHCP relay relates to NAT functions. Understanding that PAT overload uniquely enables many-to-one translation with port differentiation is critical for both exam success and practical network design.
KKey Concepts to Remember
- PAT overload allows multiple internal hosts to share a single public IPv4 address by using unique source port numbers to distinguish sessions.
- Static NAT provides a fixed one-to-one mapping between private and public IP addresses and does not support many-to-one address sharing.
- Private IPv4 addresses are not routable on the public Internet and require NAT to communicate externally.
- DHCP relay forwards DHCP requests between clients and servers but does not perform any IP address translation or NAT functions.
- PAT overload is the most efficient NAT method for conserving public IPv4 addresses when many internal users access the Internet simultaneously.
- In PAT, the router modifies both the source IP address and source port number to maintain session uniqueness for outbound traffic.
- Dynamic NAT uses a pool of public IP addresses and does not support many-to-one translation like PAT overload.
- Understanding the difference between static NAT, dynamic NAT, and PAT is essential for selecting the correct NAT approach in Cisco network designs.
TExam Day Tips
- Watch for words such as best, first, most likely and least administrative effort.
- Review why wrong options are wrong, not only why the correct option is correct.
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More questions from this exam
Keep practising from the same exam bank, or move into a focused topic page if this question exposed a weak area.
Question 1
A router learns the same prefix from both OSPF and EIGRP. Which route is installed by default?
Question 2
A router shows this output: R1#show ip ospf neighbor Neighbor ID Pri State Dead Time Address Interface 10.1.1.2 1 FULL/DR 00:00:34 192.168.12.2 GigabitEthernet0/0 10.1.1.3 1 2WAY/DROTHER 00:00:39 192.168.12.3 GigabitEthernet0/0 Which statement is correct?
Question 3
What is the OSPF metric called?
Question 4
A non-root switch has two uplinks toward the root bridge. One path has a lower total STP cost than the other. What role will the lower-cost uplink have?
Question 5
A router interface applies this ACL inbound: 10 deny tcp any any eq 80 20 permit ip any any A user reports that web browsing to a server by IP address fails, but ping works. Which statement best explains the behavior?
Question 6
A router learns route 198.51.100.0/24 from OSPF with AD 110 and also has a static route to the same prefix configured with AD 150. Which route is installed?
FAQ
Questions learners often ask
What does this 200-301 question test?
PAT overload allows multiple internal hosts to share a single public IPv4 address by using unique source port numbers to distinguish sessions.
What is the correct answer to this question?
The correct answer is: PAT overload — PAT is the correct approach because it allows many internal sessions to share one outside IPv4 address while distinguishing them by port numbers. In plain language, PAT gives the office an efficient many-to-one translation model that works well for ordinary user Internet access when public addresses are limited. This is different from static NAT, which gives a fixed one-to-one mapping, and from dynamic NAT pools that usually rely on multiple public addresses. The correct answer is the translation method designed specifically for shared public-address use across many sessions.
What should I do if I get this 200-301 question wrong?
Then try more questions from the same exam bank and focus on understanding why the wrong options are tempting.
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