300-410 · Question #40
300-410 Question #40: Real Exam Question with Answer & Explanation
The correct answer is A: By default, only internal OSPF routes are redistributed into BGP.. When redistributing OSPF routes into BGP, by default, only OSPF intra-area and inter-area routes are included, causing external OSPF routes to be excluded from the BGP table unless explicitly configured.
Question
Refer to the exhibit. An engineer is trying to redistribute OSPF to BGP, but not all of the routes are redistributed. What is the reason for this issue?
Options
- ABy default, only internal OSPF routes are redistributed into BGP.
- BBy default, only internal routers and external type 1 routes are redistributed into BGP.
- CBGP convergence is slow, so the route will eventually be present in the BGP table.
- DOnly classful networks are redistributed from OSPF to BGP.
Explanation
When redistributing OSPF routes into BGP, by default, only OSPF intra-area and inter-area routes are included, causing external OSPF routes to be excluded from the BGP table unless explicitly configured.
Common mistakes.
- B. This statement is incorrect because the default behavior for OSPF-to-BGP redistribution includes internal and inter-area routes, and does not specifically exclude or include E1 routes without additional configuration.
- C. While BGP convergence can be slower than IGPs, the complete absence of certain route types indicates a redistribution filtering issue, not merely a delay in propagation.
- D. Both OSPF and BGP are classless routing protocols, meaning they support variable-length subnet masks (VLSM), and there is no default restriction to only redistribute classful networks.
Concept tested. OSPF to BGP redistribution default behavior
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