mediumMultiple Choice
300-410 Practice Question: When redistributing routes between OSPF and…
When redistributing routes between OSPF and EIGRP, which of the following is a recommended best practice to prevent routing loops?
⚠ Common exam trap
300-410 often tests redistribution best practices. Candidates might think that changing administrative distance or metrics prevents loops, but the key is filtering. The trap is selecting an option that only affects path preference rather than preventing the loop entirely.
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
✓
Apply route filtering using route-maps or prefix-lists to control which routes are redistributed.
Applying route filtering using route-maps or prefix-lists is a best practice to control which routes are redistributed between OSPF and EIGRP. This prevents routing loops by ensuring that only intended routes are advertised and avoids feedback of routes back into the original protocol. It also allows for granular control over route attributes.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Use the same administrative distance for both protocols.
Why it's wrong here
Equal administrative distances remove the tie-breaker that suppresses feedback, so each protocol can prefer the other's redistributed routes, worsening loops. It tempts as a consistency measure, but matching distances would be correct when deliberately engineering deterministic path preference across protocols.
- ✓
Apply route filtering using route-maps or prefix-lists to control which routes are redistributed.
Why this is correct
Route-maps or prefix-lists filter which routes cross the redistribution boundary, preventing routes learned from one protocol being fed back into it. This satisfies the stem's loop-prevention requirement by controlling redistribution at the boundary rather than relying on administrative distance alone.
- ✗
Increase the default metric to a high value to discourage redistribution.
Why it's wrong here
Raising the seed metric only makes redistributed routes unattractive; it does not stop a route re-entering its origin protocol, which tagging and filtering prevent. It tempts because metric manipulation influences selection, but a high seed metric would be correct when deprioritising backup paths rather than blocking feedback.
- ✗
Disable route summarization on both protocols.
Why it's wrong here
Summarisation controls advertisement scope, not loop prevention; loops arise from mutual redistribution feeding routes back, countered by route tagging and filtering at redistribution points. It tempts because summarisation reduces table size, but disabling it would be correct when limiting topology churn or hiding subnets.
Visual reference
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.
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Written and reviewed by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
Last reviewed September 2026 · checked against the official Cisco exam blueprint
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