The answer is that a route to reach 10.0.0.2 is missing, because the BGP neighbor reachability requirement demands that the neighbor IP address be present in the routing table before the TCP connection can be established. Even though the configuration correctly sets ebgp-multihop 2 and specifies an update-source of Loopback0, BGP cannot initiate the session without a valid path to 10.0.0.2; without this, the session remains stuck in the Idle state. On the ENCOR 350-401 exam, this scenario tests your understanding that eBGP multihop only allows non-directly connected peers, but it does not create reachability—you must still provide a static or dynamic route. A common trap is assuming that ebgp-multihop alone solves all connectivity issues, when in fact the underlying IGP or static route is the true enabler. Remember the memory tip: “Multihop lets you talk across hops, but you still need a map to find the door.”
CCNP Enterprise Network Design Practice Question
This 350-401 practice question tests your understanding of enterprise network design. The scenario asks you to isolate a root cause — eliminate options that address a different problem before choosing. 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.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
A route to reach 10.0.0.2 is missing; the neighbor must be reachable via the routing table.
Option A is correct because for an eBGP session to establish, the neighbor IP address (10.0.0.2) must be reachable via the routing table. The configuration uses `ebgp-multihop 2` and an update-source of Loopback0, but there is no route (static or dynamic) to reach 10.0.0.2, so the TCP connection cannot be initiated. Without reachability, BGP will remain in the Idle state.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
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 route to reach 10.0.0.2 is missing; the neighbor must be reachable via the routing table.
Why this is correct
BGP requires TCP connectivity; without a route to the neighbor's IP, the session cannot form.
Related concept
Read the scenario before looking for a memorised answer.
✗
The ebgp-multihop value should be 1 for a directly connected neighbor.
Why it's wrong here
Since the update source is a loopback, ebgp-multihop is required and the value 2 is fine.
✗
The remote-as must be the same as the local AS for EBGP.
Why it's wrong here
EBGP requires different AS numbers; 65000 and 65001 are different, so this is correct.
✗
The router-id must be the same as the update-source interface IP.
Why it's wrong here
The router-id can be different; it is used for BGP identifier purposes.
Common exam traps
Common exam trap: answer the scenario, not the keyword
Cisco often tests the misconception that ebgp-multihop alone ensures connectivity, but the trap here is that candidates forget BGP requires IP reachability in the routing table for the neighbor address, not just a configured multihop value.
Detailed technical explanation
How to think about this question
BGP uses TCP port 179 to establish sessions, and the neighbor IP must be reachable via the routing table for the TCP three-way handshake to succeed. When using ebgp-multihop, the TTL in IP packets is set to the specified number of hops (default 1 for eBGP), and the update-source ensures the source IP matches the configured neighbor's expected peer IP. In real-world scenarios, this is common when peering over loopback interfaces for redundancy, requiring a route to the neighbor's loopback (e.g., via IGP or static route).
KKey Concepts to Remember
Read the scenario before looking for a memorised answer.
Find the constraint that changes the correct option.
Eliminate answers that are true in general but not in this case.
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.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
How this comes up in practice
A network engineer at a university connects two campus buildings via a fibre link. Both routers run OSPF, but no adjacency forms — even though both routers can ping each other. The engineer finds one router is in area 0 and the other in area 1. OSPF adjacency requires matching area numbers, hello/dead timers, and network type. IP reachability alone is not enough.
What to study next
Got this wrong? Here's your next step.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Enterprise Network Design — This question tests Enterprise Network Design — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: A route to reach 10.0.0.2 is missing; the neighbor must be reachable via the routing table. — Option A is correct because for an eBGP session to establish, the neighbor IP address (10.0.0.2) must be reachable via the routing table. The configuration uses `ebgp-multihop 2` and an update-source of Loopback0, but there is no route (static or dynamic) to reach 10.0.0.2, so the TCP connection cannot be initiated. Without reachability, BGP will remain in the Idle state.
What should I do if I get this 350-401 question wrong?
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
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Question Discussion
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