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352-001 · Question #628
352-001 Question #628: Real Exam Question with Answer & Explanation
The correct answer is D: By using route tags. Route tags are the standard mechanism to prevent routing loops when multiple routers are simultaneously redistributing routes between different routing protocol domains.
Question
When a multiprotocol routing environment is designed to have several routers redistributing among the routing domains, how can routing loops be avoided?
Options
- ABy implementing spanning tree
- BBy activating split horizon
- CBy using the AS-path attribute
- DBy using route tags
Explanation
Route tags are the standard mechanism to prevent routing loops when multiple routers are simultaneously redistributing routes between different routing protocol domains.
Common mistakes.
- A. Spanning Tree Protocol operates at Layer 2 to prevent Ethernet switching loops and has no relevance to Layer 3 routing loops introduced by redistribution between routing protocols.
- B. Split horizon prevents loops within a single distance-vector routing domain by not advertising a route back out the interface it was learned on; it does not function across different routing protocol boundaries where redistribution occurs.
- C. The AS-path attribute is a BGP-specific loop prevention mechanism that only applies to BGP peering sessions and is unavailable in generic multiprotocol redistribution scenarios involving OSPF, EIGRP, or other IGPs.
Concept tested. Route tags to prevent redistribution routing loops
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