H12-821_V1.0 · Question #766
In the BGP system, by default, BGP will automatically aggregate imported routes.
The correct answer is B. FALSE. B is correct because BGP does not automatically aggregate (summarize) imported routes by default - each route is advertised individually as a distinct prefix, exactly as it was learned or imported. Route aggregation in BGP must be explicitly configured using vendor-specific…
Question
Options
- ATRUE
- BFALSE
How the community answered
(44 responses)- A20% (9)
- B80% (35)
Explanation
B is correct because BGP does not automatically aggregate (summarize) imported routes by default - each route is advertised individually as a distinct prefix, exactly as it was learned or imported. Route aggregation in BGP must be explicitly configured using vendor-specific commands (e.g., aggregate-address in Cisco IOS), and even then, behavior depends on additional flags like summary-only. This distinguishes BGP from some IGPs that can perform automatic summarization at classful boundaries.
Why A is wrong: Claiming BGP auto-aggregates confuses it with older IGP behavior (like RIPv1/EIGRP's classful auto-summary feature) - BGP was designed for precise prefix control in inter-domain routing, where automatic summarization would be dangerous and unpredictable.
Memory tip: Think "BGP = Bring Every Prefix" - BGP is intentionally explicit and granular. Any aggregation requires a deliberate configuration decision, because in the global routing table, advertising the wrong summary can black-hole traffic for millions of users.
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