hardMultiple Choice
300-410 Practice Question: Examine this configuration on Router R6: router…
Examine this configuration on Router R6:
router ospf 1
redistribute eigrp 100 subnets default-information originate always
What is a likely problem with this configuration?
⚠ Common exam trap
The trap here is assuming that 'always' is required for the default route to be advertised, when in fact it removes the safety check that prevents advertising a default when none exists — the exact opposite of what most candidates assume.
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 router will advertise a default route into OSPF even if it does not have a default route itself, potentially causing blackholing.
The 'default-information originate always' keyword forces OSPF to originate a default route (0.0.0.0/0) into the OSPF domain unconditionally, regardless of whether the router actually has a default route in its routing table. Without the 'always' keyword, OSPF only advertises a default route if one already exists locally. Using 'always' can cause traffic to be forwarded toward R6 and then dropped (blackholed) because R6 has no valid default path.
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 'default-information originate always' command is not allowed with redistribution.
Why it's wrong here
OSPF permits 'default-information originate always' alongside redistribution; the two commands operate independently and cause no conflict. It is tempting because redistribution and default origination both inject routes, but the actual fault lies in the missing metric or metric-type values for the redistributed EIGRP routes.
- ✓
The router will advertise a default route into OSPF even if it does not have a default route itself, potentially causing blackholing.
Why this is correct
The always keyword forces OSPF to originate a default route unconditionally, even when no default route exists in the routing table. Traffic matching it is forwarded to a next hop that cannot deliver it, producing blackholing. Removing always would require an actual default route first.
- ✗
The 'subnets' keyword is missing for EIGRP redistribution.
Why it's wrong here
The 'subnets' keyword is present in the redistribution statement, so this is not the fault. It is tempting because omitting 'subnets' genuinely blocks classful-only redistribution of subnetted routes, which would be the problem in a configuration lacking that keyword.
- ✗
The redistribution will only work if EIGRP routes have a metric set.
Why it's wrong here
OSPF redistribution uses a default metric of 20 if not specified, but it will still work.
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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JA
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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