hardMultiple ChoiceObjective-mapped
300-410 Practice Question: An engineer configures EIGRP named mode on two…
An engineer configures EIGRP named mode on two routers in an MPLS L3VPN. The routers are directly connected and can ping each other. The engineer notices that the EIGRP adjacency forms but then the neighbor relationship goes down and the routers become stuck-in-active (SIA) for certain routes. The engineer checks the logs and sees no errors. What is the most likely explanation?
Answer choices
Why each option matters
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
The 'metric weights' (k-values) are mismatched between the two routers, causing query propagation to fail.
In EIGRP named mode, the default hello interval and hold time are different from classic mode. Named mode uses a default hello interval of 5 seconds and hold time of 15 seconds, while classic mode uses 5 and 15 as well, but the key difference is that named mode uses a different metric calculation (wide metrics) by default. However, the most common edge case causing SIA in named mode is that the 'metric weights' or 'k-values' must match between neighbors. If one router is using named mode with default k-values (1,0,1,0,0) and the other is using classic mode with different k-values (e.g., 1,0,1,0,0), the adjacency will form but queries may not be processed correctly, leading to SIA. Additionally, named mode requires the 'address-family' configuration to be consistent. A more specific edge case is that named mode uses a different 'graceful-restart' mechanism by default, which can cause issues if not supported on both sides.
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 'metric weights' (k-values) are mismatched between the two routers, causing query propagation to fail.
Why this is correct
Correct. EIGRP requires matching k-values between neighbors. If they differ, the adjacency may form but queries can be dropped, leading to SIA.
- ✗
The 'auto-summary' command is enabled on one router, causing route summarization to break the adjacency.
Why it's wrong here
Incorrect. Auto-summary is disabled by default in named mode and would not cause SIA; it would cause routing loops or missing routes.
- ✗
The 'passive-interface' command is applied to the interface, preventing the adjacency from forming.
Why it's wrong here
Incorrect. A passive interface would prevent the adjacency from forming at all, not cause SIA after forming.
- ✗
The 'bandwidth' setting on the interface is set to a very low value, causing the EIGRP metric to be too high for the route to be installed.
Why it's wrong here
Incorrect. Low bandwidth would affect metric calculation but not cause SIA; SIA is related to query propagation.
Quick reference
Routing Protocol Comparison
| Protocol | Metric | Max Hops | Algorithm | Type |
|---|---|---|---|---|
| RIP v2 | Hop count | 15 | Bellman-Ford | Distance vector |
| OSPF | Cost (bandwidth) | Unlimited | Dijkstra (SPF) | Link state |
| EIGRP | Composite metric | Unlimited | DUAL | Hybrid |
| IS-IS | Cost | Unlimited | Dijkstra | Link state |
| BGP | Policy / attributes | Unlimited | Path vector | Path vector |
RIP's 15-hop limit makes it unsuitable for large networks. OSPF and EIGRP dominate modern enterprise deployments.
Go deeper
Related to this question
Learn chapter
OSPF Neighbor Adjacency and Basics
Key term
MPLS Layer 3 VPN
A technology that uses Multiprotocol Label Switching to create secure, scalable virtual private networks that connect multiple sites at the network layer, where the service provider manages routing between customer sites.
Key term
LDP Protocol
LDP, or Label Distribution Protocol, is a protocol that routers use to automatically exchange labels that enable MPLS (Multiprotocol Label Switching) to create fast, efficient paths for data packets across a network.
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JA
Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
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