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350-401 Practice Question: Which three statements about BGP route reflectors…
Which three statements about BGP route reflectors are true? (Choose three.)
⚠ Common exam trap
350-401 often tests the misconception that route reflectors modify AS_PATH for loop prevention; the correct mechanisms are ORIGINATOR_ID and CLUSTER_LIST.
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
✓
Route reflectors allow iBGP speakers to advertise routes learned from other iBGP speakers without requiring a full mesh.
Option A is correct because a route reflector relaxes the iBGP full-mesh requirement by reflecting routes learned from one iBGP peer to other iBGP peers (its clients and non-clients), so speakers no longer need direct sessions with every other iBGP speaker. Option C is correct because route reflectors can be arranged in a hierarchy: a route reflector can itself be a client of a higher-level route reflector, allowing large ASes to scale beyond a single cluster. Option D is correct because the CLUSTER_ID attribute (a 4-byte value, often derived from the router ID) identifies the cluster and lets a route reflector detect and drop routes that have already been reflected, preventing loops within the cluster. Option B is not correct because route reflector clients do not need to be fully meshed with each other; they only peer with the route reflector, which is the whole point of the design. Option E is not correct because loop prevention in route reflection is handled by ORIGINATOR_ID and CLUSTER_ID (and CLUSTER_LIST), not by modifying AS_PATH, which is used for inter-AS loop prevention in eBGP.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
Route reflectors allow iBGP speakers to advertise routes learned from other iBGP speakers without requiring a full mesh.
Why this is correct
Route reflection removes the iBGP full-mesh requirement: the reflector re-advertises routes learned from one client to other clients and non-clients. This directly satisfies the scalability constraint of avoiding a full mesh between all iBGP speakers.
- ✗
A route reflector client must be fully meshed with all other clients in the same cluster.
Why it's wrong here
Reflector clients peer only with the reflector, which is the entire purpose of the design; requiring a full mesh among clients reinstates the scalability problem reflectors solve. It is tempting because iBGP speakers normally must be fully meshed, but that rule is precisely what route reflection relaxes.
- ✓
The route reflector can be a client of another route reflector.
Why this is correct
Route reflectors support hierarchical designs, so a reflector can itself act as a client of a higher-level reflector. This satisfies the stem's requirement that the statement be true, enabling multi-level clusters without a full mesh.
- ✓
The cluster ID is used to prevent routing loops in a route reflector environment.
Why this is correct
The cluster ID, carried in the CLUSTER_LIST attribute, tags routes reflected within a cluster; a route reflector discards any update whose CLUSTER_LIST already contains its own cluster ID, preventing loops between redundant reflectors in the same cluster. This directly satisfies the stem's loop-prevention requirement.
- ✗
The route reflector modifies the AS_PATH attribute to prevent loops.
Why it's wrong here
Route reflectors propagate iBGP routes by relaxing the full-mesh requirement; loop prevention relies on ORIGINATOR_ID and CLUSTER_LIST attributes, not AS_PATH modification. It is tempting because AS_PATH is BGP's familiar loop-prevention mechanism, but that applies to eBGP, not reflector clusters.
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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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