This 300-410 practice question tests your understanding of device management. This is a configuration task: choose the command set that satisfies every stated requirement. Small differences — like 'secret' vs 'password' or 'transport input ssh' vs 'all' — change whether the answer is correct. After answering, compare your reasoning against the explanation and wrong-answer breakdown below. Once you have made your selection, read the full explanation to reinforce the concept and understand why each distractor is designed to mislead on exam day.
An engineer configures iBGP between two routers in the same AS. The BGP table shows the prefix, but it is not installed in the routing table. The IGP does not carry the prefix. Which is the most likely explanation?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue: "most likely"
Why it matters: Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
The BGP synchronization rule is enabled, and the prefix is not in the IGP, so BGP does not install the route.
Synchronization requires that the prefix be reachable via IGP before BGP installs it; if not, the route remains in the BGP table but not the routing table.
B
The next-hop is unreachable because of a missing static route.
Why wrong: While next-hop reachability is required, the scenario specifically states the IGP does not carry the prefix, which is the synchronization issue.
C
The BGP route is filtered by an inbound route-map.
Why wrong: The route is in the BGP table, so it is not filtered.
D
The maximum-paths limit is exceeded.
Why wrong: Maximum-paths affects load balancing, not route installation.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
The BGP synchronization rule is enabled, and the prefix is not in the IGP, so BGP does not install the route.
BGP synchronization rule (default enabled in older IOS versions) requires that the prefix must be present in the IGP before it is installed in the routing table. If the IGP does not carry the prefix, BGP will not install it even if learned via iBGP. This edge case often surprises engineers who assume iBGP routes are always installed.
Key principle: NAT direction and interface roles matter as much as the IP address mapping. Inside/outside designation controls which traffic is translated.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
✓
The BGP synchronization rule is enabled, and the prefix is not in the IGP, so BGP does not install the route.
Why this is correct
Synchronization requires that the prefix be reachable via IGP before BGP installs it; if not, the route remains in the BGP table but not the routing table.
Clue confirmation
The clue word "most likely" in the question point toward this answer.
Related concept
Static NAT maps one inside address to one outside address.
✗
The next-hop is unreachable because of a missing static route.
Why it's wrong here
While next-hop reachability is required, the scenario specifically states the IGP does not carry the prefix, which is the synchronization issue.
✗
The BGP route is filtered by an inbound route-map.
Why it's wrong here
The route is in the BGP table, so it is not filtered.
✗
The maximum-paths limit is exceeded.
Why it's wrong here
Maximum-paths affects load balancing, not route installation.
Common exam traps
Common exam trap: NAT rules depend on direction and matching traffic
NAT is not only about the public address. The inside/outside interface roles and the ACL or rule that matches traffic are just as important.
Trap categories for this question
Scenario analysis trap
While next-hop reachability is required, the scenario specifically states the IGP does not carry the prefix, which is the synchronization issue.
Detailed technical explanation
How to think about this question
NAT questions usually test address translation, overload/PAT behaviour, static mappings and whether the right traffic is being translated. Read the interface direction and address terms carefully.
KKey Concepts to Remember
Static NAT maps one inside address to one outside address.
PAT allows many inside hosts to share one public address using ports.
Inside local and inside global describe the private and translated addresses.
NAT ACLs identify traffic for translation, not always security filtering.
TExam Day Tips
→Identify inside and outside interfaces first.
→Check whether the scenario needs static NAT, dynamic NAT or PAT.
→Do not confuse NAT matching ACLs with normal packet-filtering intent.
Key takeaway
NAT direction and interface roles matter as much as the IP address mapping. Inside/outside designation controls which traffic is translated.
Real-world example
How this comes up in practice
A small business has 20 workstations on the 192.168.1.0/24 network and one public IP from its ISP. The router uses PAT (NAT overload) so all 20 devices share one public address using different source ports. NAT questions test whether you understand the four address terms and which direction each translation applies.
Related glossary terms
Concepts from this question explained
These glossary pages explain the core terms tested in this 300-410 question in full detail.
Review the four NAT address types (inside local, inside global, outside local, outside global), PAT port overload, and static vs dynamic NAT use cases. Then practise related 300-410 NAT questions on configuration and troubleshooting.
Device Management — This question tests Device Management — Static NAT maps one inside address to one outside address..
What is the correct answer to this question?
The correct answer is: The BGP synchronization rule is enabled, and the prefix is not in the IGP, so BGP does not install the route. — BGP synchronization rule (default enabled in older IOS versions) requires that the prefix must be present in the IGP before it is installed in the routing table. If the IGP does not carry the prefix, BGP will not install it even if learned via iBGP. This edge case often surprises engineers who assume iBGP routes are always installed.
What should I do if I get this 300-410 question wrong?
Review the four NAT address types (inside local, inside global, outside local, outside global), PAT port overload, and static vs dynamic NAT use cases. Then practise related 300-410 NAT questions on configuration and troubleshooting.
Are there clue words in this question I should notice?
Yes — watch for: "most likely". Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
What is the key concept behind this question?
Static NAT maps one inside address to one outside address.
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Question Discussion
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