Question 1hardmultiple choice
Full question →hardmultiple choiceObjective-mapped
Exhibit
Configured: interface G0/0 ip nat inside interface G0/1 ip nat outside No translations appear in 'show ip nat translations'.
Exhibit: Users report intermittent internet access after PAT was configured. The inside and outside interfaces are marked correctly. Which missing configuration is the most likely cause?
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
No ACL and nat overload statement identifying inside source addresses
Correct choice.
B
Distractor review
No DHCP pool on the outside interface
Distractor.
C
Distractor review
No CDP enabled on the router
Distractor.
D
Distractor review
No syslog server configured
Distractor.
Common exam trap
Common exam trap: answer the scenario, not the keyword
A frequent exam trap is believing that configuring the inside and outside interfaces alone is enough for PAT to function correctly. Candidates may overlook the necessity of an ACL that explicitly identifies the inside local addresses for translation. Without this ACL and the corresponding NAT overload statement, the router cannot perform address translation, causing intermittent or failed internet connectivity. This mistake often occurs because the interface roles are visible and seem sufficient, but the translation logic depends on the ACL match. Understanding that PAT requires both interface roles and an ACL-based NAT overload rule is critical to avoid this pitfall.
Technical deep dive
How to think about this question
Port Address Translation (PAT), a form of Network Address Translation (NAT), allows multiple devices on a private network to access the internet using a single public IP address. PAT achieves this by mapping multiple inside local IP addresses to a single inside global IP address, differentiating sessions by assigning unique source port numbers. This process requires the router to know which inside addresses to translate, which is done through an access control list (ACL) that defines the range of inside local IP addresses eligible for translation. When configuring PAT on Cisco routers, the NAT statement must reference an ACL that identifies the inside local addresses to be translated. Additionally, the router interfaces must be correctly designated as inside or outside to ensure proper translation direction. The NAT overload keyword enables port translation, allowing multiple sessions to share one public IP. Without the ACL and the NAT overload command, the router cannot translate the inside addresses, resulting in intermittent or no internet access for users. A common exam trap is assuming that simply marking interfaces as inside and outside is sufficient for PAT to work. However, without the ACL and NAT overload statement, the router does not know which addresses to translate or how to handle multiple sessions. In practical networking, failing to configure the ACL or NAT overload leads to failed translations and connectivity issues, highlighting the importance of complete NAT configuration for reliable internet access.
KKey Concepts to Remember
- Port Address Translation (PAT) requires a correctly configured access control list (ACL) to identify inside local IP addresses for translation.
- NAT overload uses a single public IP address to translate multiple private IP addresses by differentiating sessions with unique port numbers.
- The NAT configuration must include both inside and outside interface designations to properly translate traffic between private and public networks.
- Without an ACL specifying which inside addresses to translate, the router cannot apply NAT overload, causing intermittent or failed internet access.
- PAT translates multiple inside local addresses to a single inside global address by using port numbers to maintain unique sessions.
- Configuring a DHCP pool on the outside interface is unrelated to PAT functionality and does not affect NAT translation.
- Cisco Discovery Protocol (CDP) is a Layer 2 protocol used for device discovery and does not impact NAT or PAT operations.
- Syslog server configuration is used for logging and monitoring but does not influence NAT translation or internet access.
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?
Port Address Translation (PAT) requires a correctly configured access control list (ACL) to identify inside local IP addresses for translation.
What is the correct answer to this question?
The correct answer is: No ACL and nat overload statement identifying inside source addresses — PAT needs both the inside and outside interface roles and a NAT statement referencing an ACL that identifies the inside local addresses. Without the ACL match and NAT overload rule, translation does not occur for user traffic.
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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