Question 1mediummultiple choice
Full question →mediummultiple choiceObjective-mapped
Exhibit
ip nat inside source list 10 interface g0/0 overload access-list 10 permit 192.168.10.0 0.0.0.255 ! interface g0/0 ip address 203.0.113.2 255.255.255.252 ! interface g0/1 ip address 192.168.10.1 255.255.255.0 ip nat inside
Exhibit: A router is configured for NAT overload, but translations never appear when inside users browse the internet. Which issue is most likely?
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
The outside interface is missing the ip nat outside command
Without inside and outside roles, overload translations will not build correctly.
B
Distractor review
The ACL used by NAT must deny inside addresses
The NAT ACL should usually match the inside local addresses to be translated.
C
Distractor review
PAT requires DHCP on the inside interface
PAT does not require DHCP.
D
Distractor review
NAT overload works only with OSPF-learned routes
NAT is independent of the routing protocol choice.
Common exam trap
Common exam trap: answer the scenario, not the keyword
A frequent exam trap is overlooking the necessity of explicitly configuring the outside interface with the ip nat outside command. Candidates often assume NAT overload works automatically once NAT is enabled, but without defining inside and outside interfaces, the router lacks context to translate addresses. Another trap is misunderstanding the role of ACLs in NAT; the ACL should permit inside local addresses, not deny them. Additionally, some mistakenly believe that NAT depends on routing protocols like OSPF or requires DHCP on the inside interface, which is incorrect. These misconceptions can lead to selecting wrong answers despite correct NAT configuration elsewhere.
Technical deep dive
How to think about this question
Network Address Translation (NAT) overload, also known as Port Address Translation (PAT), allows multiple inside local IP addresses to be mapped to a single inside global IP address by using different port numbers. This technique conserves public IP addresses and enables multiple devices on a private network to access the internet simultaneously. For NAT overload to function correctly, the router must identify which interfaces are inside and which are outside to apply translation rules properly. The router uses the commands ip nat inside and ip nat outside to designate interfaces accordingly. The inside interface connects to the private network, while the outside interface connects to the public network or internet. If the outside interface is not configured with ip nat outside, the router cannot correctly translate inside local addresses to inside global addresses, resulting in no NAT translations appearing. This misconfiguration prevents the router from building the NAT translation table, causing inside users to fail when browsing the internet. A common exam trap is assuming that NAT overload will work without explicitly configuring inside and outside interface roles. Candidates might also confuse ACLs used for NAT with deny rules, or believe that routing protocols like OSPF affect NAT operation. In practice, NAT operates independently of routing protocols and DHCP presence. Correct interface role assignment is essential for NAT to function, and missing ip nat outside on the external interface is the most frequent cause of translation failures.
KKey Concepts to Remember
- NAT overload allows multiple inside local IP addresses to share a single inside global IP address by using unique port numbers for each session.
- The router requires explicit configuration of inside and outside interfaces using ip nat inside and ip nat outside commands to correctly apply NAT translations.
- Without the ip nat outside command on the external interface, the router cannot build NAT translation entries, causing inside users to fail internet access.
- ACLs used in NAT configurations must permit inside local addresses for translation and should not deny them, ensuring proper NAT operation.
- NAT overload operates independently of routing protocols such as OSPF and does not require DHCP on the inside interface to function.
- The NAT translation table remains empty if interface roles are missing or reversed, preventing any NAT translations from occurring.
- Correct interface role assignment is essential for NAT to identify traffic direction and perform address translation accurately.
- Misconfiguring NAT interface roles is a common cause of NAT failures and a frequent exam trap in CCNA 200-301 scenarios.
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?
NAT overload allows multiple inside local IP addresses to share a single inside global IP address by using unique port numbers for each session.
What is the correct answer to this question?
The correct answer is: The outside interface is missing the ip nat outside command — NAT needs the inside and outside interfaces marked correctly. If those roles are missing or reversed, the router has no context for translating traffic and the NAT table stays empty.
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.
Discussion
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