300-320 · Question #257
A BGP network is having difficulty scaling with the full mesh peer requirement. What two iBGP alternates can scale BGP appropriately? (Choose two.)
The correct answer is B. route reflectors C. confederations. iBGP requires a full mesh of peering sessions by default to prevent routing loops (since iBGP learned routes are not re-advertised to other iBGP peers). In a network with n routers, this requires n(n-1)/2 sessions, which becomes unmanageable at scale. Route Reflectors (RR)…
Question
A BGP network is having difficulty scaling with the full mesh peer requirement. What two iBGP alternates can scale BGP appropriately? (Choose two.)
Options
- Acommunities
- Broute reflectors
- Cconfederations
- Dpeer groups
- Epeer templates
How the community answered
(21 responses)- B90% (19)
- D5% (1)
- E5% (1)
Explanation
iBGP requires a full mesh of peering sessions by default to prevent routing loops (since iBGP learned routes are not re-advertised to other iBGP peers). In a network with n routers, this requires n(n-1)/2 sessions, which becomes unmanageable at scale. Route Reflectors (RR) solve this by designating specific routers to reflect iBGP updates to other peers (clients), eliminating the need for full mesh. Confederations solve this by dividing the AS into sub-ASes that use eBGP between them internally, reducing the full mesh scope to within each sub-AS. Options D (peer groups) and E (peer templates) reduce configuration complexity but do NOT reduce the number of required peering sessions - they don't solve the full mesh scaling problem. Option A (communities) is a policy and tagging mechanism, not a topology solution.
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