The answer is that R2 is using a route-map to set the EIGRP metric to 4294967295, which is the maximum 32-bit metric value and effectively marks the routes as unreachable. This causes R1 to receive the routes via the IPsec VPN tunnel and store them in the topology table in a passive state, but the metric of 4294967295 prevents them from being installed in the routing table, even though the neighbor adjacency is fully established. On the Cisco CCNP ENARSI 300-410 exam, this scenario tests your understanding of EIGRP metric manipulation and the distinction between the topology table and the routing table—a common trap is assuming a passive route is always usable. Remember that a route must have a feasible successor or be the successor itself to be installed; a metric of all ones (4294967295) is the EIGRP equivalent of “infinity.” Memory tip: think of 4294967295 as the “poison” metric—if you see it, the route is dead on arrival.
300-410 IPsec Site-to-Site VPN Practice Question
This 300-410 practice question tests your understanding of ipsec site-to-site vpn. 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.
R1 and R2 are connected via an IPsec VPN tunnel. They are running EIGRP over the tunnel. R1's show ip eigrp neighbors shows R2 as up, but R1's show ip eigrp topology shows all routes from R2 in passive state. However, R1's show ip route does not have any EIGRP routes from R2. What is the root cause?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
R2 is using a route-map to set EIGRP metric to 4294967295, making routes inaccessible.
The EIGRPmetric of 4294967295 is the maximum possible metric (32-bit value), effectively making the route unreachable. When R2 applies a route-map to set this metric, R1 receives the routes but considers them inaccessible, so they appear in the topology table as passive (since the neighbor is up and the route is learned) but are not installed in the routing table. This matches the symptoms: neighbor adjacency is established, routes are in the topology table, but no EIGRP routes appear in the IP routing table.
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.
✓
R2 is using a route-map to set EIGRP metric to 4294967295, making routes inaccessible.
Why this is correct
EIGRP routes with metric 4294967295 are considered unreachable and are not installed in the routing table, even though they appear in topology.
Related concept
Read the scenario before looking for a memorised answer.
✗
EIGRP variance is set to 1, preventing load balancing.
Why it's wrong here
Variance affects load balancing, not route installation.
✗
The tunnel interface is down on R2.
Why it's wrong here
If tunnel were down, EIGRP neighbor would not be up.
✗
R1 has a passive interface for the tunnel.
Why it's wrong here
Passive interface would prevent R1 from sending hellos, but neighbor is up.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates see routes in the EIGRP topology table as passive and assume they are installed in the routing table, but Cisco tests the distinction between the topology table (which stores all learned routes) and the routing table (which only stores feasible successors with valid metrics).
Detailed technical explanation
How to think about this question
EIGRP uses a composite metric based on bandwidth, delay, reliability, load, and MTU, with a maximum value of 4,294,967,295 (2^32 - 1). A route with this metric is considered unreachable because it exceeds the feasibility condition and is not installed in the routing table, though it remains in the topology table as a learned route. In real-world scenarios, route-maps are sometimes misconfigured to set metrics incorrectly, or used intentionally to filter routes by making them inaccessible, which can lead to this exact symptom.
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.
Related glossary terms
Concepts from this question explained
These glossary pages explain the core terms tested in this 300-410 question in full detail.
IPsec Site-to-Site VPN — This question tests IPsec Site-to-Site VPN — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: R2 is using a route-map to set EIGRP metric to 4294967295, making routes inaccessible. — The EIGRP metric of 4294967295 is the maximum possible metric (32-bit value), effectively making the route unreachable. When R2 applies a route-map to set this metric, R1 receives the routes but considers them inaccessible, so they appear in the topology table as passive (since the neighbor is up and the route is learned) but are not installed in the routing table. This matches the symptoms: neighbor adjacency is established, routes are in the topology table, but no EIGRP routes appear in the IP routing table.
What should I do if I get this 300-410 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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